Labour faces further defections from its campaign to hold a stronghold seat in a by-election, amid signs of fracturing of support for the party among ethnic minority voters.

The Times understands that the Conservatives are preparing to announce that another group of senior local Labour figures in Ealing Southall are to switch sides, including a prominent member of the Hindu community.

It comes after the defection yesterday of a sixth Labour councillor, a Muslim, to David Cameron’s party, a day after five Labour colleagues on Ealing council, all Sikhs, quit to join the Tories before the parliamentary by-election on July 19.

More defections would fuel the factionalism and in-fighting that have riven Labour’s local party in Ealing Southall, one of the largest in Britain with 1,800 members, after rows over an abandoned plan for an all-woman shortlist followed by a fast-track selection for a parliamentary candidate.

The question facing Labour is whether such moves are driven by Southall’s heady brand of local politics, where feuding and changing allegiance are commonplace, or represent more evidence of a breach between Labour and minority communities, which for a generation haved enjoyed strong mutual ties.

Most troubling for Labour are divisions among Sikhs in Southall, which is home to Britain’s longest-established Sikh community. They comprise 23 per cent of the electorate in the constituency, which has the largest Sikh temple outside India.

The most prominent defector to the Tories, Southall councillor Gurcharan Singh, resigned after he was refused a place in the final shortlist of two from which Labour’s candidate was selected.

He told The Times yesterday: “I don’t think the Labour Party is ready yet to have a turban-wearing Sikh as an MP.” He pointed out darkly that, of the five candidates rejected from Labour’s “long list”, three were turban-wearing Sikhs.

Yesterday he was busy helping to set up a Tory campaign base in the travel agency run by Manjit Singh, a fellow former Labour councillor, whose windows were bedecked with giant posters for the Tory candidate.

Gurcharan Singh said that he had been told “at least 100 times” by the late Piara Khabra, the MP for Ealing Southall whose death triggered the by-election, that he was to be his anointed successor as MP but was blocked first by plans for an all-woman shortlist and then by the special selection procedure for chosing by-election candidates. Mr Khabra was from a Sikh family but was a largely secular figure.

In the event Labour members chose as their candidate Virendra Sharma, a Brahmin or high caste Hindu and Gurcharan Singh’s long-time rival, to fight the seat. Opponents claim that he was not an active councillor and a “Southall machine politician”.

Two other local Sikhs were nominated to stand as independent by-election candidates but one, Kuldeep Singh Grewal, was persuaded to return to the Labour Party while another, Gulbash Singh, abandoned his campaign and backed the Conservatives.

Mr Sharma presented himself as a unifying figure who would represent all communities, including Sikhs. He said: “If you look at the teachings of Sikhism that is based on equality, secularism and the community. I am part of the community here. I am also part of secularism.” Suggestions of a breakdown in support for Labour among the Sikh local community were hotly disputed by senior party figures, who are conscious of how Liberal Democrats targeted Muslim voters at the last election with their opposition to the Iraq war.

Tom Watson, a Labour whip and veteran of past bruising by-elections, who is helping to direct Labour’s campaign in Southall, said: “Southall is the spiritual home of British Sikhism and they are Labour. For them to go to the Tories would be like going to a South Yorkshire coal mining areas in the 1980s and think they are going to vote for Mrs Thatcher.”

To reinforce Labour’s links with local Sikhs, David Miliband, the Foreign Secretary, visited two Sikh temples in Southall yesterday, joining worshippers during prayers at one and walking to the other for a brief meeting with community leaders.

Others dismissed the defections as motivated by the frustrated ambition of Gurcharan Singh, their ringleader, and said that Southall politics had long had a volatile character.

Mr Khabra’s predecessor, the left-wing Labour MP Sid Bidwell, was forced to fight off repeated attempts to deselect him in the mid1980s by local Labour factions who wanted to replace him with an Asian MP.

While trying to keep a lid on internal party feuding, Labour has two headaches. The Conservative candidate Tony Lit, a Sikh whose father founded Sunrise Radio in Southall, is mounting a high-profile, well-funded campaign with many posters in shops and five loud speaker cars touring Southall streets uring people to vote for him. Opponents question, however, whether such activity is being followed through in contact with voters.

Meanwhile, the Liberal Democrats are mounting a huge operation to produce and deliver newspapers and leaflets highlighting their opposition to the Iraq war and the local credentials of their candidate, Nigel Bakhai. Hundreds of the party’s volunteers have flocked to Southall from across the country to support the campaign.

Melting pot

The constituency by numbers:

— 47.8% Asian

— 37.6% White

— 8.9% Black

— 35% Christian

— 23.2% Sikh

— 13.3% Muslim

— 12.4% Hindu

Source: 2001 Census

Times Recommends

• Time-worn Freddie gives up Test matches
• Brighton company 'involved in cyber attack'
• The art of survival: it’s all in the mind