Lena Jeger was a lively, popular figure in the Palace of Westminster for more than 40 years. Although her heart was on the left of the Labour Party she was never doctrinaire. Even though she never expected senior office her friends were surprised that, unlike some of her Bevanite colleagues, she failed to receive even a junior post in any of the Harold Wilson governments.

This may have been because of her inclination to socialise when she could, though it was noticeable that when she had a job to do — as when she chaired the Labour conference at Blackpool in 1980 — she produced an immaculate performance. As MP for Holborn and St Pancras South, a constituency with substantial areas of deprivation, she was noted for her active concern over a whole range of issues, particularly those which touched the lives of the elderly and otherwise vulnerable sections of society, such as the poor and badly housed.

In the Lords she was latterly a vigorous presence, particularly in opposition to the Government of Tony Blair on matters of conscience and socialist principle. She had been associated with a number of defeats inflicted on the Government, over such issues as restricting the defendant’s right to trial by jury and the privatisation of National Air Traffic Control Services.

Lena May Jeger was born in 1915. Her father was a postman who worked for many years in the Holborn and St Pancras area she was later to represent in Parliament.

She was educated at South-gate County School, Middle-sex, and Birkbeck College, University of London, and began her career in the Civil Service. She joined in 1936 in one of the lower grades in Customs & Excise, but was soon promoted, her breakthrough coming when she was posted first to the Ministry of Information and then the Foreign Office.

This led to her becoming during the Second World War assistant editor of British Ally, the newspaper produced by the Churchill Government for circulation inside the Soviet Union. She was sent to the British Embassy in Moscow, and there she proved that she was a naturally gifted journalist with skills that were developed after the war on The Manchester Guardian (now The Guardian) where some of her feature articles are still remembered.

She had been a dedicated socialist since her schooldays. On her return to Britain she became a Labour member of St Pancras Borough Council and in 1951 she was elected to the London County Council.

By then she had married Dr Santo Jeger, who became MP for Holborn and St Pancras South. But Dr Jeger, a well-loved general practitioner, was a Jew and she was a gentile and the marriage was one reason for a breach with some members of his family. He died unexpectedly in 1953 and Jeger was chosen to defend the seat. The constituency was highly marginal, and with the Churchill government in confident mood and Labour split by the Bevanite insurrection, it was regarded as a highly probable Tory gain.

Labour had established little organisation in the constituency but the London Labour Party, built up by Herbert Morrison, was then a formidable force and threw in its best agents, headed by Morrison’s own former agent. Jeger fought a courageous by-election to retain the seat and, surprisingly, to increase the majority.

It remained a risky constituency, however, and in the 1955 general election she held it by only 931. In 1959 it fell, inevitably, in a good Conservative year, Jeger losing by 656 votes, and incidentally providing Geoffrey Johnson Smith with the opportunity to begin his long parliamentary career. He lost it to her in turn in 1964 and, helped by occasional boundary changes and the Jeger name, she retained the seat without difficulty in four subsequent general elections.

During her five years of exile from the Commons Jeger returned to The Guardian but she never left politics. Almost immediately after her parliamentary defeat she was elected to the Labour Party’s National Executive Committee and on two later occasions she topped the poll in the women’s section.

When she won back Holborn and St Pancras South in 1964 (it became Camden, Holborn and St Pancras South in 1974) she concentrated her efforts in the Commons on housing and Cyprus — two major issues in her constituency, which had more of its share of bad housing and contained a fair number of Cypriots. She became a hardworking chairman of a government working party on sewage disposal which produced a radical report.

In 1978, well in advance of the general election, she announced she would not be standing again, saying: “I prefer to leave while people are asking why I am going than why I am staying.” When she left the House for the last time she summed up the procedure: “You fill an old carrier bag with your coat-hang-er, a spotty little mirror, the spare shoes for lobby-tramping and a half-empty bottle of face cleanser which tried to take the midnight grit out of the wrinkles . . .” She also observed she would have to start buying postage stamps again: “For you have finished with OHMS — and she with you.”

But HMS had not finished with her because almost at once she became Baroness Jeger. She acted first as opposition spokesman on health in the Lords and then on social security, and she held court at a table in the Guest Room in the Upper House with all the aplomb she had displayed when presiding at the Strangers’ Bar in the Commons.

In the Lords she was a thorn in the side of what she considered the authoritarian tendency of new Labour policies. In 2000 she was one of only three Labour peers who inflicted a second defeat on the Government over its plans to sell off National Air Traffic Control Services. In 2003 she was among 12 whose votes helped to defeat the Government over its plan to restrict a defendent’s right to jury trial in complex fraud cases, or in cases where where there was a risk of jury tampering.

Lena Jeger had no children.

Baroness Jeger, former Labour Member of Parliament and opposition frontbench spokesman, House of Lords, was born on November 19, 1915. She died on February 26, 2007, aged 91