Birmingham's claim to be championing the country's toughest crackdown on postal vote fraud was challenged yesterday when Labour said new measures to combat ballot-rigging did not go far enough.

Sir Albert Bore, the leader of the Labour opposition group on the city council, accused Conservative and Liberal Democrats of rejecting a more rigorous assault on vote tampering.

All three parties announced last week that they had agreed, together with the police, a ban on representatives from political parties handling completed postal ballots.

The move, which is voluntary, goes a step further than guidance issued by the Electoral Commission, which allows voting slips to be collected when there is no other way of getting a vote to the post box.

However, Sir Albert gave details of three further sanctions which Labour has unilaterally imposed on its own candidates and party workers.

The additional measures, which were not approved by the Conservatives and Liberal Democrats and do not appear in the council's new protocol on ballot rigging, are: A form to be filled in to identify every occasion that a party worker helps to organise a postal vote; A ban on party representatives entering electors' homes once postal ballot papers have been delivered; No more than one teller or polling agent from each party to go within 100 yards of polling stations on election day

The council protocol, which will be in place for the May 4 elections, is designed to head off a repeat of the events of June 2004, when Birmingham became the centre of extensive vote-rigging allegations by Labour supporters.

With the deadline for applications expiring earlier this week, the city council will send out 59,000 postal votes for May 4. On this occasion candidates, agents and canvassers will be unable to collect completed postal ballots or deliver them to polling stations. Sir Albert's allegations were rejected by Paul Tilsley, leader of the Liberal Democrat group and deputy leader of the council.

Coun Tilsley (Lib Dem South Yardley) said the protocol had been drawn up by the police and the council elections office and represented the most practical way to combat fraud. Labour's additional proposals were unenforceable, he claimed.

"We all know what is going on here," he added. "Labour is trying to divert attention away from its own appalling record on postal vote fraud by pretending to act tough."

Sir Albert said: "The protocol as it exists is simply about not handling postal ballots. We wanted to go further with a clause preventing party representatives from entering houses once papers have been sent out.

"We are talking about a no-visit policy. We want to avoid individuals going into homes and being subject to allegations that they are encouraging postal votes to be filled in in a certain way.

"We have had no indication from the Conservatives or Liberal Democrats as to why they were unwilling to pursue these issues."

City Council chief executive Stephen Hughes, who is also the returning officer, said: "We want the people of Birmingham to be able to exercise their vote confidently and properly. We welcome all of the support we have received from the police and the political parties in ensuring that this election is conducted fairly and in accordance with the rules."

West Midlands Police Assistant Chief Constable Stuart Hyde said: "All agencies involved in the election process are responsible for ensuring election fraud does not occur.

"We are continually working with partners to ensure the integrity of the election process and welcome this protocol as a further means to support the progress that has already been achieved."