Battlebus 2015
Expenses relating to the Conservative Battlebus were reportedly undeclared in local campaign returnsToby Melville-Pool/Getty Images

As MPs start campaigning ahead of the snap general election on the 8 June, several Conservatives still face the possibility of prosecution.

Fourteen police forces have sent files to the Crown Prosecution Service (CPS) relating to the Tory 2015 ''battle bus'', which has been alleged to have helped Tory candidates breaking strict spending limits on elections.

The CPS is currently reviewing the evidence and considering whether to charge the MPs with breaking the election spending limits, which were put in place to prevent candidates with wealthy backers from gaining an unfair advantage during elections.

The snap general election may play a part in the future for some of those MPs and agents who are under investigation.

A spokesperson for the CPS confirmed that any charges would have to be made before the date of the general election.

This means the CPS's announcement must by law fall while the MPs are campaigning for re-election, before 8 June.

So far, no charges have been made against any of those being investigated.

Police forces who have sent files to the CPS relating to the spending allegations include Avon & Somerset, Cumbria, Derbyshire, Devon & Cornwall, Gloucestershire, Greater Manchester, Lincolnshire, the Metropolitan, Northamptonshire, Nottinghamshire and West Yorkshire.

Two dozen Conservatives are understood to be under investigation over claims that they did not include battle bus spending in their local campaign returns.

The Electoral Commission is also investigating the allegations in parallel to the police.

The allegations centre on whether spending on hotels for visiting activists and certain campaign material was incorrectly registered as national spending rather than locally – potentially illegitimately taking advantage of a higher spending ceiling.

A Conservative spokesman said: "We are cooperating with the ongoing investigations."