The warning comes after the President-elect sent markets into turmoil after threatening to slap huge tariffs on Canada, Mexico and China.
It has provoked fears that the UK could also be targeted when Mr Trump enters the White House in January.
The government has reportedly been wargaming how to respond if Joe Biden’s successor hits British imports in the US.
Such a move could see Britain slap retaliatory taxes on American brands including Harley Davidsons, Jack Daniel’s whiskey and Levi’s jeans.
But economist Julian Jessop warned against the idea, saying it would harm British consumers.
“It’s a stupid idea, it’s like blockading your own ports,” he said.
“Starmer should be negotiating on a trade deal with Trump. If there is a trade war you don’t join in, you find a way around it.
“We need to be peacemakers not warmongers”.
Mr Jessop, a fellow at the Institute of Economic Affairs, said he doesn’t think the UK would be a “frontline target” of the next US government.
“Our exports to the US are relatively minor in comparison to other countries, such as Canada, China and even Germany.
It comes after Mr Trump threatened to impose a 25% tariff on all goods coming from Mexico and Canada, after being inaugurated on 20 January 2025.
He also said an additional 10% tariff would be levied on China until its government cracked down on fentanyl drug smuggling to the US.
China, Mexico and Canada account for about 40% of the $3.2tn (£2.6tn) of goods it imports each year, according to official data.
His remarks have prompted fears that Britain could be hit next, a move which could trigger a major global trade war.
It is understood that UK officials have told ministers that they can revive a package of measures against the US, Politico reported.
The EU tariffs were carried over after Brexit, having initially been placed on US goods in Mr Trump’s first term in response to his levies on European steel.
They targeted US products such as Calvin Klein, Estée Lauder and American staples such as peanut butter.
Downing Street would not be drawn on how Britain would respond if tariffs are hiked.
The Prime Minister’s official spokesman said: “We look forward to working with President-elect Trump including on a wide range of his policy priorities to improve the UK-US special relationship, including when it comes to trade and investment.
“I am not going to get drawn on specific policies before he takes office, but clearly the fact that a million Americans work for UK-owned businesses and vice versa and the fact that UK-US trade was worth £304 billion in the last year, clearly that is something that we want to build on.”
Meanwhile, senior Bank of England official has suggested that massive US tariffs on Chinese imports could drag down global inflation by lowering the price of goods in other countries.
Swati Dhingra, an external member of the Bank’s rate-setting monetary policy committee, said Chinese exporters to cut their prices elsewhere to ensure they maintained current trade volumes.
“If there is the kind of big 60% type of tariff increase that’s been proposed, that will have repercussions on to world prices, and mostly on the downward direction,” she said.
She said the “textbook” impact of the world’s largest goods importer imposing such a large tariff on products from the world’s biggest exporter would be for global goods prices to fall.
Chinese firms would respond to tougher trade barriers by attempting to find buyers in alternative markets, which could lead them to lower their prices to sell similar volumes, including in the UK, she said.