The former Liberal Democrat chief secretary to the Treasury David Laws has been found guilty of breaching six House of Commons rules in a report by the parliament's standards watchdog.

But John Lyon, the parliamentary commissioner for standards, has concluded that there is no evidence to suggest Laws had broken the rules out of a desire to maximise profits.

The finding will strengthen his argument that he claimed more than £40,000 in expenses for rent paid to his partner because of a desire to keep his sexuality private.

Laws resigned from the cabinet on 29 May after admitting he made a mistake after the rules of the Commons were changed to bar such claims in 2006.

The report by Lyon was considered on Tuesday by the cross-party standards and privileges committee. The committee is expected to publish the report on Thursday, possibly with a recommendation that Laws should apologise to MPs.

It is understood Lyon has concluded that Laws broke one over-arching rule: claiming for the £950 a month in rent he paid to his partner, Jamie Lundie. The five other breaches are understood to be related to subsidiary rules broken as a consequence of the major mistake over his expenses.

Lyon is also understood to have concluded that he found no evidence to suggest Laws had made the claims to benefit himself or his partner.

Laws is likely to argue that the findings by Lyon endorse what he said when he resigned – that he broke the rules but did not do so out of a desire to maximise profits.

Nick Clegg is keen to see Laws – one of the most influential Lib Dems – return to government. But the Lib Dems acknowledge that it will be difficult for Laws to return if the criticism in the report is harsh.