Aug. 3 (UPI) — Britain’s Reform U.K. party vowed Monday that if elected it would use the Royal Navy to turn back small boats bringing migrants across from France and Belgium, in what it said would be the largest military operation in the English Channel since World War II.

The policy launched at a news conference in London calls for the military to “intercept” the boats and return them to France or Belgium, with the party claiming “Operation Fortress” had the backing of former senior military brass and that it was in line with international law because its purpose was humanitarian.

Reform U.K. Home Affairs spokesman Zia Yusuf told the BBC that it would be possible for Britain to return the migrants without agreement from France, arguing that international law required they dealt with migrants on their territory and not let them continue onto Britain.

States are permitted to pull people from the sea but can only bring them to another country with the agreement of that country.

Yusuf acknowledged the move could spark a “diplomatic argument” between Paris and London.

Under agreements with the United Kingdom, authorities on the continent prevent thousands of migrants from setting sail for England, but those that do manage it are met by U.K. Border Force and Coast Guard vessels which take the migrants aboard and bring them ashore to ports in the south of England.

The announcement came hours after new Labour Prime Minister Andy Burnham vowed he would be “relentless” in combatting small boat crossings after some 60,000 migrants overwhelmed the border of the Spanish territory of Ceuta on the north African coast on Thursday and Friday.

Britain is separated from Ceuta by the channel, several European countries and more than a thousand miles, but Burnham said his concern was with “the broader issue of the Schengen [free travel] Area and our relationship with it,” saying he would seek regular dialogue with the European Union on the matter.

The Schengen Convention of 1990 abolished border controls across 29 mostly EU member European countries. Migrants arriving in Europe are supposed to be processed in the first safe country they reach but in practice they’re often allowed to move on, via several countries, to their desired destination. Migrants wanting to get to Britain end up in northern France, or the Belgian coast.

Burnham stressed that in order to defeat people trafficking gangs organizing the boat crossings refugees needed “safe routes” of reaching Britain. Currently, people must get to Britain before they can claim asylum, an almost impossible hurdle for nationals of countries from which most migrants hail without resorting to traffickers.

The number of people crossing the English Channel in small boats fell 43% in the first seven months of this year, compared with the same period in 2025, according to Home Office data. However, numbers have fallen in all of the past four years after peaking in 2022.