A Labor government would face tough negotiations with the EU over Brexit, senior diplomats have warned.
The UK's last EU commissioner and two former British ambassadors spoke out as Sir Keir Starmer eyes closer ties with Brussels if he wins the next general election.
Lord Darroch, who was British ambassador to the EU and the US, told the Daily Telegraph: “The Commission is an extremely hard-nosed negotiator. And they pride themselves on it.
“The EU has moved on from Brexit. There are plenty of issues around Europe. And what happens next with the Brits really doesn't make the top 10.
“They expect Labor to be basically more pro-European but they also expect Labor to be extremely cautious on Europe [..] we shouldn't expect any free gifts.”
Sir Julian King, who was the last British EU commissioner before Brexit, added: “Labour have to be ready for a really nitty gritty, difficult discussion because just being nice isn't going to cut it.”
Sir Ivan Rogers, a former ambassador to the EU, warned that “some in Labor tend greatly to underestimate the difficulties it will face”.
The UK and Brussels have agreed to review the Brexit trade deal in 2026.
Sir Keir had pledged to re-write the agreement if he enters No 10 but was rebuffed by the EU.
The Labor leader wants a veterinary deal to reduce Irish Sea border checks between Britain and Northern Ireland and make trade with the bloc smoother.
But Brussels is expected to demand that the UK align with EU plant and animal health rules, as well as European Court of Justice oversight.
Sir Keir also wants to formalize foreign policy and security cooperation with the bloc, which it is understood to be open to.
The Labor leader, who backed Remain and a second referendum, has insisted he would not seek to rejoin the single market or customs union.