One of the European Commission's most senior officials has warned that the EU could "reassess" the access US financial services firms have to the single market if Donald Trump follows through with plans to roll back key regulation.

Vice president Valdis Dombrovskis hit out at Mr Trump's recent executive order which will see a review of the 2010 Dodd-Frank financial oversight law - put in place to rein in reckless financial behaviour following the 2008 banking crisis - and said the EU would take "necessary measures" to protect financial stability in Europe.

"We are sensitive to talk of unpicking financial legislation which applies carefully negotiated international standards and rules," Mr Dombrovskis said during a speech at the Bloomberg headquarters in London.

"It is difficult not to notice when the chair of the Federal Reserve is criticised for her approach to negotiating international rule and standards, or when an American president talks about 'doing a big number' on Dodd Frank."

While the US has "every right" to "redefine its national interest", Mr Dombrovskis said, "as friends and allies, Europe is entitled to gently suggest international co-operation on financial governance is in everyone's interest."

Mr Dombrovskis - who is in charge of financial stability, financial services and pushing forward plans for the EU's Capital Markets Union - warned that regulatory changes could risk existing agreements with the bloc.

US financial firms have benefited from rules that allow certain foreign industries to operate across the bloc if they are governed by regulatory regimes deemed "equivalent" to those in the EU.

It has opened the door to US businesses involved in derivatives trading, and last month resulted in an agreement that makes it easier for insurers and reinsurers to operate on both sides of the Atlantic.

"The EU has been very open to recognise that our international partners' rules are equivalent and achieve the same objective as ours. But these findings depend very much on the specific conditions of individual sectors and country at the time when the decisions are made.

"If these conditions change, we will have to reassess the situation.

European Central Bank president Mario Draghi said earlier this week that financial deregulation and expansive monetary policy were "exactly the ground on which the financial crisis developed".

The Trump administration has argued Dodd-Frank has not achieved its purpose and is an example of government over-reach.

Mr Trump dubbed Dodd-Frank a "disaster" and said he could repeal and replace the law, which also created the Consumer Financial Protection Bureau (CFPB).

But without co-ordinated regulation, Mr Dombrovskis said, hubs like New York, Frankfurt and London would be more exposed to risks imported from countries with less stringent rules, while companies would face higher compliance costs.

Businesses would also flock to regions with lower regulation, leading to under-regulated financial activity that would "put whole financial systems at risk".

"Lax regulation in one country can create conditions for inadequate regulation and contagion throughout the world."

Mr Dombrovski hailed London for proving industry can thrive under international regulation.

"Far from being held back by international rules and standards agreed in the last decade, London has been thriving. And regardless of the UK's future relationship with the EU, London will only continue to thrive on the basis of a strong international system."