Ben Gummer is one of five MPs under scrutiny over election campaign costs following a joint investigation by the Bureau of Investigative Journalism and Channel 4 News.

The documents submitted by Mr Gummer’s campaign team made no reference to T-shirts with the slogan “Vote for Ben in 2010″. In addition, his campaign manager was paid £8,750 for her efforts in the “long campaign” period – but not a penny in the “short campaign”, where spending limits begin to bite.

Mr Gummer, the Conservative MP for Ipswich, is the son of former cabinet minister John Gummer. The 32-year-old Cambridge graduate is the author of a history book and ran a small engineering firm before being elected to parliament earlier this year.

Ben Gummer’s campaign featured the professional skills of Sophie Stanbrook, who runs her own consultancy firm, and is regularly described as Ben Gummer’s “campaign manager”.

In the three months before the election is called, Mr Gummer paid Stanbrook thousands of pounds in consultancy fees as his campaign manager. She is paid every working day from the beginning of the year.

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But from the moment parliament is dissolved and the general election begins in earnest – the critical campaigning period known as the short campaign – her wage invoices disappear. As if by magic she has become an unpaid volunteer.

If Gummer had paid Stanbrook at the same rate for working during the short election campaign period then he would have been over his spending limit by as much as £1,800.

Electoral Commission guidance makes clear that unpaid voluntary work on a campaign is perfectly acceptable and does not have to be accounted for. But having examined dozens of MPs returns, the way in which Mr Gummer accounted for Ms Stanbrook is unusual.

The Conservative Party told us that: “Many staff did paid work until the dissolution of parliament and then agreed to work on a voluntary basis.”

They said there was a similar arrangement with many House of Commons staff for which there were strict guidelines, adding “to suggest an MP would frontload their staff’s salary is to interpret the parliamentary system unfairly.”

They added: “We are confident that the election expenses in question comply with the spirit and letter of election law.”

Ben Gummer election expenses – Short campaign

Related links:

• Election expenses: Five more MPs face questions