"Both sides must implement what we agreed on," von der Leyen, European Commission president, said after meeting Johnson alongside Michel, the European Council president.
"There is complete EU unity on this," she said, adding that the deal had been agreed, signed and ratified by both Johnson's government and the bloc.
The UK had insisted it wanted to take back control of its waters while EU coastal states sought guarantees that their fleets could keep fishing in British waters.
The EU-UK trade pact was provisionally applied on January 1, after nine months of tough negotiations and a last minute handshake just before Christmas last year.
The value of goods brought in from Britain fell 56%, compared to a drop of just 10.3% in imports from 27 European Union countries.
The UK left the European Union's single market at the end of last year, raising barriers to trade. That final split followed more than four years of wrangling over its terms of exit from the EU.
At a time when Brexit is focusing minds on the future of financial services, this is an area of regulatory policy that provides an opportunity for UK financial services to gain competitive advantage on the global stage.
"The speed at which vulnerabilities are remediated should be commensurate with the potential impact that a disruption would cause, and will be an area of supervisory focus," the BoE said.
We're saying there is a window of opportunity for constructive dialogue to see if we can actually get a workable solution, and I've no doubt we could get a workable solution, but it does require Brussels and Dublin to return to honouring the core guarantees of the (Belfast) Agreement.
If it doesn't happen, then they are opening a Pandora's box which leads to significant protest, to the bringing down of the Northern Ireland executive and then into a significant political crisis.
Although we recognise that many in the border industry and many businesses have been investing time and energy to be ready on time, and indeed we in Government were confident of being ready on time, we have listened to businesses who have made a strong case that they need more time to prepare.
Ensuring free and safe flow of personal data is crucial for businesses and citizens on both sides of the Channel. The UK has left the EU, but not the European privacy family.
This should be completed before the end of June, when an interim arrangement for data flows after Brexit ends.
Britain left the EU at the end of January last year, but kept its full access to the 27-nation bloc's single market until the end of 2020, when it was replaced by a trade agreement.
For the EU on average, the exit of the UK from the European Union on Free Trade Agreement terms is estimated to generate an output loss of around 0.5% of GDP by the end of 2022, and some 2.25% point for the UK.
Tensions have been rising, the Protocol is quite clearly having a damaging impact not just on the port of Larne...
We had received intelligence that there was individuals taking registration plate numbers from staff who were coming to and from the port, that's quite sinister.
Crucial talks on future ties and trade with the bloc then start in March, but break deadline after deadline as negotiators try to avert a no-deal Brexit on December 31.
The father of British Prime Minister Boris Johnson said on Thursday he was in the process of applying for a French passport to maintain his ties with the European Union after Brexit.
Stanley Johnson, a former member of the European Parliament who voted Remain in Britain’s 2016 referendum, told RTL radio he wanted to become a French citizen because of strong family links to France.