The EU has warned Sir Keir Starmer his attempt to repair relations with the bloc may fail if he does not fully implement post-Brexit agreements on Northern Ireland, it has emerged.

The Prime Minister has made rebuilding ties with Brussels a top priority since the General Election, after years of mistrust between the two sides over Brexit.

The European Commission has welcomed Sir Keir’s positive approach, but issued a list of eight tests through which the UK can “demonstrate real government commitment” to its withdrawal agreement with the EU.

The list, revealed by the Financial Times, called for the “faithful and timely implementation” of the Windsor Framework — which it described as a “cornerstone for the EU-UK relationship” — and the rights of EU citizens living in the UK.

EU diplomats told the paper the two measures would be seen as a “test of good faith” in the new relationship.

However, sources in Brussels told The Telegraph that the commission has become frustrated by the inaction in carrying out the required trade checks on shipments between Great Britain and Northern Ireland.

The Commission has also listed the need for a High Court ruling, that EU citizens in Britain should not have to make separate applications for settled status after living in the UK for five years, to be implemented in full.

The list also raised concerns about UK authorities failing to accurately certify animal and plant products, called for non-compliant consignments to be rejected by vets at the border and called for a scheme to check pets to be deployed “urgently”.

It also called for a new system to provide data on the content of parcels to be implemented as soon as possible.

“This needs to be fixed before we talk about cooperation in new areas,” one diplomat told the FT.

Sir Keir has repeatedly talked up his drive to reset relations with Europe after years of deterioration under the Conservatives. There was a slight improvement under Rishi Sunak, who last year signed the Windsor Framework to end the row over post-Brexit arrangements in Northern Ireland. But further meetings with European leaders have been a key focus of Sir Keir’s first weeks in office.

In July he hosted leaders from across the continent at a major summit in Blenheim Palace, declaring that the UK would be a “friend and a partner ready to work with you” and “not part of the European Union, but very much part of Europe”.

The Prime Minister wants to strike a security pact with the EU and address some of the trading problems under the current Brexit deal.

He has so far refused to entertain the prospect of a youth mobility deal with the bloc, which would allow young people to live, study and work across the EU, in exchange for EU citizens being able to do the same in the UK.

But sources told the FT such a deal was a priority for the bloc, alongside access to British fishing waters and the UK rejoining the Erasmus student exchange programme.

The Cabinet Office declined to comment on the specifics of the leaked document. But a Government spokesperson said: “Since taking office this government has been working to reset the relationship with our European friends, to strengthen ties, secure a broad-based security pact and tackle barriers to trade.

“We’ve had very positive engagement in our early conversations and are committed to implementing the Withdrawal Agreement, including the Windsor Framework in good faith protecting the UK internal market.”

A European Commission spokesperson said: “The EU is committed to a positive agenda with the UK, based on the full respect, and the faithful and timely implementation of the withdrawal agreement, including the Windsor framework, and the trade and cooperation agreement, which are the cornerstone for the EU-UK relationship.”

© The Independent