Conservative Party co-chairman Baroness Warsi was guilty of only a "minor" breach of the ministerial code in relation to a trip to Pakistan with a business partner, the Prime Minister's adviser on ministerial interests ruled.

Sir Alex Allan said Lady Warsi accepted that she should have informed officials of her relationship with Abid Hussain - a second cousin of her husband - and had already issued an apology.

David Cameron said he was satisfied that Sir Alex's report found that she did not at any point use her office for any personal financial gain.

Sir Alex said that when he interviewed Lady Warsi a number of "related issues" arose - including her wish for clearer guidance on travelling with spouses.

"Baroness Warsi's office was clearly stretched when it came to handling arrangements for overseas travel, especially given that her overseas visits tend to involve issues and arrangements which are out of the ordinary for regular departmental ministers," he said.

"I therefore recommend that the Cabinet Office and the Foreign Office should discuss and agree arrangements for providing advice and support to Baroness Warsi in relation to the ministerial code."

Lady Warsi said tonight in a statement: "I have always maintained that I have never misused my ministerial office for personal or financial gain.

"The allegations on this matter were untrue and unsubstantiated and I am pleased that Sir Alex Allan's report has confirmed that.

"The last month has been a difficult time for me and my family and I am pleased I can now move on from this period and get on with the job that I am privileged to do."

Mr Cameron referred the case Sir Alex earlier this month following press reports of a visit she made to Pakistan in July 2010, shortly after she became a minister.

Mr Hussain - who was involved with Lady Warsi and her husband in a restaurant supply firm called Rupert's Recipes - was among a number of individuals from the UK Pakistani diaspora recommended by Lady Warsi's office to help organise two "outreach" events as part of her programme.

Mr Hussain attended and spoke at both events although he was not part of the official UK delegation and Sir Alex said he did not receive any government funding for his travel or accommodation.

Sir Alex said that when she became a minister, Lady Warsi had declared her shareholding in Rupert's Recipes to the Cabinet Office but it was not included in the published list of ministerial interests as "it was considered de minimus and of no relevance to her ministerial portfolio".

However the Cabinet Office was not aware of the identity of the other shareholders in the firm "including in particular Mr Hussain".

Sir Alex said he was satisfied that if Lady Warsi had declared her business relationship with Mr Hussain, it would not have been seen as a barrier to him helping to organise the visit.

"Nonetheless," he said, "she should have been more aware of the perception of a conflict of interest, and the potential criticism which could arise."

On the same grounds, he said that she should have made officials aware of their business relationship when she became aware that Mr Hussain had been invited to an Eid reception at No 10 in November 2010.

In his final recommendation to Mr Cameron, Sir Alex concluded: "Any action you decide to take in the light of the facts of this case is of course a matter for you, but I record my view that the breach of the code was a minor one, and that Baroness Warsi did not use her office for personal financial gain.

"I note that you have already accepted Baroness Warsi's apology."