The number of migrants trying to get into the Eurotunnel terminal near Calais has fallen to about 150 a night, the operator says, down from a high of 2,000 at the end of last month.
The company said extra security measures recently put into place were making a "real difference".
But it said the number of attempted break-ins remained "unacceptable".
Migrants in Calais make nightly bids to cross the Channel into the UK, causing delays on some cross-Channel services.
The UK government says it is spending £7m to improve security at Eurotunnel, but accepts there is still more work to do.
Extra fencing, paid for by the UK, has been erected, aimed at making it harder for migrants to get onto the platforms and trains at the terminal.
Eurotunnel said an increase in police numbers is keeping some migrants from getting near the terminal, leading to fewer disruptions for passenger and freight trains.
It also said the fall in numbers of attempted break-ins was a "huge improvement", adding that most of those gaining access to the terminal were being apprehended by security guards.
However, the operator does believe that some migrants are still managing to make it to Britain.
Previously agreed security measures between the British and French authorities include:
- Extra private security guards, funded by the UK, to boost an existing 200-strong team
- An increased presence of French police on the borders throughout the summer
- Additional fencing, funded by the UK, installed around the Eurotunnel perimeter as required, with higher boundaries and extra layers where necessary and a large metal barrier to protect Eurotunnel platforms
- Extra CCTV, infra-red detectors and floodlighting to secure key segments of the perimeter fence