It comes as the immigration minister Chris Philp travelled to Paris today to discuss the crisis with his French counterpart.
Prime Minister Boris Johnson has said he wants to work with the French to stop the illegal crossings which have surged in recent weeks.
Asked by Sky News what the PM meant, Mr Argar said: “What he’s looking at, quite rightly, is greater flexibility in our ability to negotiate something which allows us greater flexibility in returning people who have come here illegally, have been through due process.”
Yesterday an RAF plane began flying surveillance missions over the Channel.
More than 4,000 migrants have made it so far this year, with at least 597 arriving between Thursday and Sunday.
The Home Office has also formally requested the help of the Royal Navy.
The Government has come under pressure from its own MPs after good weather and calm seas led to hundreds of people trying to cross the world’s busiest shipping lane.
Natalie Elphicke, the Tory MP for Dover, said she expected today’s meeting to lead to a “stepping up” of existing measures such as “patrols, drones, surveillance and tackling criminal gangs”.
Ms Elphicke also called for a “bilateral agreement” with France on returns.
However, former British ambassador to France Lord Ricketts suggested the UK should help France stop migrant boats leaving their shores instead of intercepting them in the Channel.