By William James

LONDON (Reuters) - British trade‎ minister Liam Fox urged ministers from more than 30 Commonwealth countries to resist "seductive" trade protectionism on Thursday, eyeing the network of mostly former colonies as a way to boost post-Brexit trade.

The plea comes weeks, possibly even days, before Prime Minister Theresa May begins the process of Britain's divorce from the European Union. That will force the world's fifth largest economy to find new trade partners at a time when globalization is under fire from populist, nationalist politics‎ in several major economies.

‎Speaking at an event organized to try and reboot the Commonwealth -- a 52-country alliance which includes the likes of India, Australia and Canada -- as a champion of free-trade, Fox warned of a "rising chorus of protectionism".

"Protectionism can be a seductive but false friend. I have described it as the Class A drug of the trading world: it can make you feel good at first but you pay a terrible price in the long term," he said.

Brexit and the election of U.S. President Donald Trump have thrown relations with Britain's two largest trading partners up in the air, with the EU expected to drive a hard bargain in exit talks and Trump's nationalist rhetoric tempering enthusiasm about the terms of any Anglo-American trade deal.

Fox said he wanted strengthen trade with the Commonwealth and see the group "lead the defense of free trade".

But Britain's attempts to woo Commonwealth partners have drawn criticism from some quarters.

Former minister and ex-Goldman Sachs chief economist Jim O'Neill told the Politico website this week that a trade deal with New Zealand would make "zero difference" to Britain's future in terms of trade.

Thursday's meeting is the first to bring Commonwealth ministers together to focus on trade. The organization hopes to boost trade between its members to $1 trillion dollars by 2020, from around $500 billion now.

Jonathan Marland, head of the Commonwealth Enterprise and Investment Council which organized the meeting, said the change in global mood could aid networks like the Commonwealth which have shared legal systems and business culture.

"In a world where globalization is potentially retrenching with the change of attitude in the American government and obviously Brexit ... there is a great opportunity" for the group, he told reporters.

(Editing by Catherine Evans)