An emergency pre-trial review into the case of six Birmingham Labour councillors accused of postal vote fraud will take place at the High Court in London today.

The decision to summon all sides in the Aston and Bordesley Green election petitions was taken following the announcement on Monday that Labour Party solicitors would no longer represent the accused. A hearing to consider allegations that the councillors were responsible for ballot rigging at the 2004 council elections is due to begin in Birmingham on Monday.

The six - Muhammad Afzal, Mohammed Islam and Mohammed Kazi in Aston and Shafaq Ahmed, Shah Jahan and Ayaz Khan in Bordesley Green - deny any wrongdoing.

The Labour Party said that the behaviour of some Labour activists and supporters of other parties in the two wards may have "fallen short of the high standards that the electors have the right to expect".

Liberal Democrat supporters in Aston, who submitted the election petition, will ask Commissioner Richard Mawrey QC, the trial judge, to declare the Aston Labour councillors improperly elected.

They believe the evidence is so strong that Mr Mawrey should take the unusual step of declaring the three losing Liberal Democrat candidates victors of the 2004 election.

The more usual procedure if a judge rules a result unsafe would be to order an election re-run. But Ayoub Khan, a former Lib Dem Aston councillor, said: "Our position is that we have always alleged personal corruption against the candidates."

The political balance would shift if the Liberal Democrats picked up all six seats in Aston and Bordesley Green.

Labour's strength would fall from 53 councillors to 47, the Liberal Democrats would have 34 and the Conservatives 39.

In that event, Lib Dem leaders might demand an additional cabinet seat.