A Conservative MEP has had his motives questioned by the EU’s executive after delaying a vote on Brussels legislation that would force online platforms to remove terrorist content.

In a letter from the European commission to Dan Dalton, leaked to the Guardian, the EU’s executive called on him to “rise to the occasion” and lamented “time lost”, with the current parliament to have its final session in April.

The commission’s proposal, which is backed by the British government, would set a one-hour limit on the removal of terrorist content from the time at which it has been reported. If in breach of the regulation, platforms could be fined up to 4% of their global turnover.

Dalton is the “rapporteur” for the legislation, responsible for finding a majority on his parliamentary committee and putting the draft to a vote to allow it to progress towards becoming law.

In his letter to the MEP, the British security commissioner, Sir Julian King, described the issue as a “matter of urgency” in light of the failure of online platforms to swiftly take down footage of the terrorist attack in New Zealand.

“We have been asking internet companies to show responsibility in tackling terrorist content online, but we also need to rise to the occasion,” the commissioner wrote to Dalton.

“There is still a possibility for the co-legislators to reach agreement on this vital proposal during this mandate of the European parliament. We therefore urge you to take the necessary steps to that end, in the interest of the security of all citizens.”

King told reporters in an aside during a press conference in Brussels earlier this week that he had “difficulty understanding the motivation of colleagues in the European parliament who are seeking to delay and time-out our outstanding legislative proposal on a regulation on terrorist content online”.

Sources close to Dalton, who in 2017 had his hotel and transport costs paid for by Google during a two-day trip to Zurich, said the MEP had held off from holding a vote on the proposal as he did not believe there was yet sufficient support to allow it to pass.

But the legislation needs to be passed by the civil liberties committee before being voted on by the chamber as a whole, with time short before the end of the parliamentary term.

Sources on the committee said they had implored Dalton to ask his colleagues to vote on the issue, so it might be passed on along its legislative journey towards becoming law, but the MEP had declined. The legislation is expected to be put to a vote on 1 April.

The Counter Extremism Project, a non-governmental organisation, has also written to Dalton expressing its “deep disappointment”.

Dalton, who will be without a job once the UK has left the EU, said in a statement: “The commission clearly wants another piece of legacy legislation before [Jean-Claude] Juncker’s mandate ends. But it’s not up to them to tell directly elected MEPs when they should be voting on something.

“This draft law raises huge questions about free speech. We first need to bridge the gaps between the different political parties, but the aim is to find a compromise soon.”

A spokesman for Dalton said no considerations beyond the need to construct cross-party support for the legislation had caused him to delay putting it to a vote.

The trip to Google’s offices in Zurich had been arranged by the EU40 initiative, an organisation that seeks to expand the horizons of MEPs under the age of 40. The trip involved a visit to the Cern research laboratory. The costs of Dalton’s hotel – the Marriott in Zurich – and travel by coach were met by Google. He paid for his flight home and the visit was declared in the appropriate way.