The Conservatives have been rebuked by the elections watchdog after breaching spending rules during the 2017 election campaign.

The party has been ordered to improve how it records election costs after the Electoral Commission found “systemic” failings.

Similar action has also been taken against the Liberal Democrats for breaches of electoral rules.

Both parties have agreed to legally-binding “enforcement undertakings”.

They will be given a deadline to make improvements, including better training and guidance for staff and changes to systems for recording spending, to ensure they comply with election rules.

They have avoided a financial penalty by agreeing to make the changes, but the Electoral Commission could impose a fine at a later date if action is not taken by the deadline.

It came after the watchdog found that the parties had filed inaccurate returns and paid some invoices later than legally allowed. The Conservatives also failed to provides evidence for some payments made during the campaign.

Louise Edwards, the Electoral Commission’s director of regulation, said: “Political parties that contest elections and spend millions of pounds trying to persuade voters to support them must ensure they submit complete and accurate spending returns.

“Both the Conservative Party and the Liberal Democrats have a history of failing to do this.

“Rather than fine the parties, we have chosen to work with them to improve their compliance by requiring them to spend their money on improving systems and training staff.”

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A Conservative Party spokesperson said: “We are working collaboratively with the Electoral Commission to improve systems and procedures to avoid any past technical administrative issues recurring moving forwards.

“As a means of future regulation, we hope that our undertaking will assist the commission when dealing with other political parties.”

A Liberal Democrat spokesperson said: “The Liberal Democrats are continually striving to improve compliance with the provisions of the Political Parties Elections and Referendums Act 2000 (PPERA) and the Representation of the People Act 1983 (RPA).