Labour politicians have long had an uneasy relationship with private and selective schools, which many party members continue to view as contrary to Labour principles.

The most brazen to break with Labour ideology was Diane Abbott, the fiery left-wing MP for Hackney North and Stoke Newington, who admitted to hypocrisy after sending her son, then 12, to the £10,000-a-year City of London School instead of a comprehensive in her constituency.

“It is indefensible,” admitted Ms Abbott at the time. “I have campaigned for nearly ten years on what happens to black children in British schools. But at the end of the day I had to put my reputation as a politician against my son, and I chose my son.”

Several government figures close to Tony Blair also opted for private schools at stages in their children’s education.

Baroness Morgan of Huyton, then Mr Blair’s director of government relations, also sent her son to the City of London School after failing to secure places for him at two comprehensives in Wandsworth. She defended her decision, saying she had “put my son first”.

Anji Hunter, Mr Blair’s former “gatekeeper” at No 10, who reputedly read the pulse of middle England on his behalf, sent her son to board as a sixth-former at Ardingly College after he attended Warden Park, a comprehensive near Haywards Heath in West Sussex.

An illustration of the hostility to private education traditionally held by Labour activists came when Mr Blair tried to secure a seat in the Commons for his former flatmate, Lord Falconer of Thoroton, now Lord Chancellor.

The seat of Dudley East was vacated shortly before the 1997 general election by the Labour MP John Gilbert, who was later raised to the peerage. But when Charlie Falconer, as he then was, came for interview with the local party, he was asked about the fact that all four of his children were at private schools. What would happen if he were selected as their candidate, they asked.

“Nothing, they stay put,” Lord Falconer replied. He was rejected, and had to rely on Mr Blair’s patronage to bring him into the Lords.

Mr Blair, who was educated at Fettes College in Edinburgh, faced severe criticism himelf when Leader of the Opposition for rejecting state schools in his borough of Islington and sending Euan, his eldest son, across the capital to the grant-maintained London Oratory school in Fulham. Four years ago it also emerged that the Blairs had paid for private tuition for two of their children.

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