The percentage of boats stopped from crossing has dropped nearly 10 per cent since the landmark deal was signed
Just over a quarter (28.7 per cent) of attempts to cross from northern France to southern England were stopped by French police in the 13-week period since the deal was implemented in August.
This is a departure from the 38 per cent which were stopped in an equivalent period before the deal was struck.
Data released by The Telegraph show that French authorities successfully prevented 5,281 crossings in the 13 weeks before the deal.
That fell to 4,633 in the 13 weeks afterwards.
As part of the deal, the French government pledged to adopt new tactics to tackle crossings including by stopping dinghies while they were in water within 300 metres of the shoreline.
But these tactics have been delayed amid fears they could endanger lives.
Shadow Home Secretary, Chris Philp, said the French performance was “lamentable”.
He added: “Preventing only a quarter of now record migrant crossings is woeful and embarrassing and the new French police training around ‘no life jacket’ tactic now needs to end.
“Those very same migrants filmed in Calais as the French police stand by are the police ushering illegal immigrants on a public bus towards embarkation points. We have seen 2,000 illegal immigrants cross in a four-day period recently. The Government has lost control of our borders.”
A Home Office spokesman said: “We are working closely with the French on the Joint operations and with our European partners to tackle illegal migration.
"This Government will continue to work with our partners to prevent boats before they set out and to scale up the removal of illegal migrants.”
When announcing the deal, Sir Keir said the agreement will see migrants arriving by small boat will be "detained and returned to France in short order".
Despite this pledge, two of the few migrants deported under the scheme have since been detected returning to Britain again via small boat.
