Theresa May has refused to apologise for the Conservative expenses scandal at the last election, insisting the party’s candidates “did nothing wrong”.

The Prime Minister brushed off a record fine imposed by the elections watchdog to claim Tories about to face the voters had emerged from the affair without a stain.

Ms May was asked to say sorry after the Crown Prosecution Service (CPS) – while pressing no charges against Tory candidates – found “evidence to suggest the returns may have been inaccurate”.

Meanwhile, the Metropolitan Police is still investigating the former Tory treasurer, Simon Day, for allegedly “knowingly or recklessly making a false declaration”.

But, on the campaign trial, Ms May said: “The CPS has decided – they are an independent body – they have decided that no charges will be brought against any candidate in relation to this matter.

“Candidates did nothing wrong. It’s very important and I repeat that – I have said it many times – candidates did nothing wrong.”

Speaking in Nottinghamshire, the Prime Minister claimed the CPS statement had “confirmed what we believed all along” – that “local spending was properly reported”.

She declined to repeat the incendiary claim made by her party chairman, Patrick McLoughlin, who attacked “politically motivated and unfounded complaints that have wasted police time”.

However, she did say: “Of course, police time has been taken up in relation to this issue. Those who made those complaints will have to consider the basis on which they made those complaints.”

The Prime Minister did acknowledge the record £70,000 fine imposed by the Electoral Commission for inaccurate returns. The watchdog also criticised the Tories for not cooperating with its investigation.

Referring to punishments imposed on other parties, she said: “We have paid our fine and I sincerely hope that the other parties are paying theirs.”

Nicola Sturgeon, the SNP First Minister – who had claimed the general election was called in part because Ms May feared prosecutions – reacted with fury to her claim that the SNP had also broken rules.

“PM should apologise for this attempt to smear @theSNP – unlike Tories, we abide by rules and have never been fined by Electoral Commission,” she tweeted.

Jeremy Corbyn said he was “surprised” that no Conservatives have been charged as part of the investigation into election expenses – adding “money can’t buy power”.

The Labour leader said the Electoral Commission and the Crown Prosecution Service are “independent”, adding: “They have to make a judgement on it.

“But our election laws must be enforced and must be adhered to.

“There are strict spending limits for a reason so that money can’t buy power, only votes in the ballot box should be able to get power.”

Earlier, the CPS said no charges were being brought against 2015 Conservative candidates for breaches of expenses rules, after it examined files from 14 police forces.

However – despite Ms May’s claims they “did nothing wrong” – it said there was evidence of inaccurate spending declarations, but it did not meet the test for further action.

The statement said: “In order to bring a charge, it must be proved that a suspect knew the return was inaccurate and acted dishonestly in signing the declaration.

“Although there is evidence to suggest the returns may have been inaccurate, there is insufficient evidence to prove to the criminal standard that any candidate or agent was dishonest.”

The allegations centred on the expenses claims of the party’s 2015 battle bus, which triggered the £70,000 fine at a national level.

Candidates were accused of labelling spending on hotels and campaign material as national spending – potentially allowing them to increase their local constituency campaigning without breaking spending rules.