British Prime Minister David Cameron's electoral guru, Australian Lynton Crosby, has rejected a Labour attack on his personal tax affairs as a "made up negative story".

On Thursday the British Labour Party called on Mr Crosby to explain his links to two companies based in Malta after the Evening Standard reported that Mr Crosby was a director of Rutland Ltd and a shareholder in Rutland Holdings Ltd and that both companies shared a Maltese address with Bentley Trust (Malta), a financial services firm offering "legitimate mitigation" of tax.

While the Labour Party did not accuse Mr Crosby of anything illegal, tax minimisation, both legal and illegal, has been a hot topic in the weeks and months leading up to May's UK general election, with the government criticised over the HSBC Swiss Leaks tax evasion scandal, and last week's debate over the "non-domicile" loophole for wealthy British residents who want to protect overseas earnings from the tax man.

Labour's Margaret Hodge, who has chased companies such as Amazon, Google and Starbucks over tax avoidance in her role as chairman of a parliamentary committee told the Evening Standard that few people in the Conservative party wielded as much power as Lynton Crosby.

"Looking at the sheer complexity of his network of offshore interests, it is difficult to see what purpose these arrangements can possibly serve other than to avoid tax," she said.

In response to questions from the newspaper, a spokesman for Mr Crosby said, "Any claim, or attempt to claim, Mr Crosby has attempted to reduce his tax liability in the UK is malicious and libellous and will be treated as such."

The attack on Mr Crosby came in a week that Labour extended its election lead on the Conservatives in two polls. Labour's promise on "non-dom" tax proved popular in some polls, however Labour's shadow chancellor Ed Balls was revealed to have opposed the idea only a few months ago, saying it "would cost Britain money".

The claims are the same as those made a year-and-a-half ago, in 2013, by the vociferously Labour-leaning British tabloid the Daily Mirror, which had launched a tirade against Malta in a clearly politically-motivated bid to discredit British Prime Minister David Cameron's election adviser.

In an article week entitled "David Cameron's election guru Lynton Crosby uses mysterious offshore tax haven", The Mirror had taken Mr Crosby, and by default David Cameron, to task over his ownership of the companies in Malta set up in 2011 to provide, "consultancy and technical services".

"David Cameron's election guru owns and runs a mysterious offshore company in Malta," The Mirror reported, adding, "The link between Lynton Crosby and the notorious tax haven [i.e. Malta] will cause acute embarrassment to the PM, who has described legal ploys to avoid tax as 'morally wrong'."

Margaret Hodge, head of the Public Accounts Committee, had even said, "It beggars belief that the Tories are taking advice from a man who operates out of a notorious tax haven."

But without giving any information whatsoever about the operations of the company, or how it was set up to allegedly avoid UK tax, the paper latched upon the sole fact that Crosby holds ownership of a company in Malta as the main piece of incriminating evidence.

A spokesman for CTF Partners, Crosby's main holding company, had replied at the time that, "Rutland is a legitimate company, which fulfils all its tax obligations in Malta. It has never done any business in the UK or paid any dividends to anyone in the UK. It has not received fees from any UK company, body, or individual. Any claim, or attempt to claim, that it was set up, or is used, to avoid paying UK tax is categorically wrong and highly damaging."