Labour’s deputy leader has warned Digital Minister Matt Hancock to avoid any conflict of interests in his future dealings with ex-chancellor George Osborne, now Evening Standard editor.

Tom Watson said Mr Osborne would be expected to seek to influence ministers on media policy in his new role, and urged Mr Hancock to excuse himself from any matters relating to the Standard.

Mr Osborne has faced calls to quit as an MP after he accepted the editorship.

But he insists he can do both jobs.

In a letter to the digital and culture minister of state, Mr Watson pointed to the long-standing personal and professional relationship Mr Hancock had enjoyed with Mr Osborne.

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“It is a matter of public record that your first job in politics, in 2005, was as an economic advisor to Mr Osborne, who was then the shadow chancellor,” he wrote.

“You later became Mr Osborne’s chief of staff. These roles and the contacts you will have made through holding them, were no doubt helpful to you as you successfully sought selection as Conservative parliamentary candidate for West Suffolk, the constituency you have represented as an MP since 2010.”

Mr Watson stressed that there was “no secret, and no shame, in a Conservative MP being a loyal ally of his former boss and powerful patron” – but he warned that as a minister he will now have responsibility for policy areas in which Mr Osborne and his new employer have a commercial interest.

Politics and journalism

He argued that, as the Standard’s editor, Mr Osborne “can be expected to seek to influence ministers on media policy in line with his views and the views of his paper’s proprietor Mr Alexander Lebedev, both in the pages of the newspaper and in meetings with ministers.

“You would be one of the chief targets of any such attempts to influence media policy,” he said.

“Your long-standing relationship with Mr Osborne means that any ministerial decisions you make from now on which affect media policy will be subject to accusations of a conflict of interest which it will be difficult for you to disprove.”

Mr Osborne’s new job has caused controversy after he said he intends to combine the editorship role with that of representing his Cheshire constituency of Tatton – 190 miles from the capital.

But in an open letter to his constituents, Mr Osborne said: “There is a long tradition of politics and journalism mixing. One of the greatest newspaper editors ever, CP Scott, combined editing the Manchester Guardian with being an MP.

“In our age, politicians from Iain Macleod and Richard Crossman to, of course, Boris Johnson have combined the role of editor and Member of Parliament,” the Knutsford Guardian reported.