The Government is coming under fresh pressure to let the people of Birmingham decide whether they want an elected mayor after a petition demanding a referendum hit the 10,000-signature mark.

The response represents just over a quarter of the names needed to force a reluctant city council to hold a poll.

But the Department for Communities and Local Government can still order the council to stage a referendum, even if the petition falls short of five per cent of the city electorate - about 36,000 signatures.

Legislation setting out the rules for changing the governance of a local authority makes it clear that the minister responsible can require a mayoral referendum to be held if it can be shown the idea has "substantial support".

The 10,000 signatories come six months after The Birmingham Mail launched its mayoral campaign, and it is understood the paper will seek to convince ministers that the backing of more than 10,000 people would represent more than enough support from electors to justify a referendum.

Executives are expected to point out that a petition demanding the refurbishment of New Street Station, which it ran in conjunction with the council, was described as a huge success by civic leaders when it attracted 7,000 signatures.

With six months to go until the mayoral petition must be handed to the council, there is growing confidence that more than 20,000 signatures may be achievable. The paper is stressing it is not campaigning for an elected mayor, but merely wishes to give the people of Birmingham an opportunity to vote on the matter.

The success of the campaign has been boosted by Birmingham Citizens, an umbrella group of community organisations which says it exists "to give ordinary people a voice in the city", which has been working with the paper to maximise grass roots support for a referendum. More than half of the signatures have been collected by Birmingham Citizens representatives.

Signatures and addresses on the petition are yet to be validated, although sample checks have demonstrated a 95 per cent accuracy rate.

Signatories must be on the Birmingham electoral register.

The growth of the petition is potentially embarrassing for the city council's Conservative-Liberal Democrat leadership, which has been outspoken against the campaign and privately doubted whether more than 5,000 signatures could be achieved.

Council leader Mike Whitby has refused to countenance a referendum, stating that he believes there is no public support for an elected mayor and a poll would be a waste of money. A spokesman for Coun Whitby (Con Harborne) said: "Our position on this issue remains unchanged. If there is genuine public support for a referendum then the Government have legislated to provide a mechanism for that to be demonstrated.

"In Birmingham's case it needs 36,000 people to sign a petition and submit it to the city council within a year."

The council's opposition Labour group believes a referendum should be held.

Deputy leader Ian Ward (Lab Shard End) said: "Whichever way you look at it, 10,000 signatures is an impressive number. The Government should recognise this as significant support for a referendum."

The business community is split over the idea. Birmingham Forward, representing the professional services sector, is keeping an open mind pending the results of a membership survey, while Birmingham Future, which is Forward's young professionals arm, believes a mayoral referendum should be held.

Birmingham Chamber of Commerce and Industry says the mayoral debate is a distraction.