Insurers are calling on the Government to "get on with it" and strike a deal now on the transition period after Brexit.
The director general of the Association of British Insurers accused ministers of "over-complicating" discussions over the transition, expected to last up to two years after the date of Brexit in March 2019.
Delaying agreement on the transition will destroy its value for companies, which will be forced to put Brexit contingency plans into place if a deal is not reached soon, Huw Evans warned.
Britain and the EU agreed in December to work towards agreement in March on a transition period, during which the UK is expected to follow Brussels rules in their entirety while losing the power to influence them.
But over the past weeks, disputes have arisen over issues such as the precise duration of the transition and the rights of EU nationals coming to the UK while it is in place.
Speaking to the ABI annual dinner in London, Mr Evans said: "Before Christmas ... I was encouraged by the preliminary deal which looked to finalise the terms of a standstill transition by March this year.
"Since then, we seem to have gone backwards with, at times, our own Government seeking to over-complicate a deal by putting extra demands on the table such as extra restrictions on EU citizens.
"The time for hard bargaining is surely over the terms of the final deal, not the interim period, especially when an early agreement is needed to help businesses and regulators manage the huge changes involved and is so important for clarity with customers on issues such as the EHIC (European Health Insurance Card) and travel insurance and motor and fleet insurance and green cards.
"So my message to the Government and MPs tonight is simple - 'Please, get on with it'.
"A transitional agreement only reached at the 11th hour as part of horse-trading over the final agreement will be of no value to businesses that have had to implement contingency plans by then instead. We need a straightforward transitional and we need it now."
The UK is the world's largest exporter of insurance products, exporting £11.58 of insurance and pensions services for each £1 it imported between 2013-15, said the ABI. More than 320,000 people are employed in the industry in the UK, two-thirds of them outside London.