The head of a British parliamentary committee criticised the government on Tuesday for advising companies to prepare for Brexit without first telling them what to expect when the country quits the European Union.

Nicky Morgan, a lawmaker from the ruling Conservative Party who heads the Treasury Committee, said the government’s advice was “extraordinary” given the uncertainty around Brexit for businesses.

The government had responded to a report by her committee by saying that businesses should try to understand how regulatory change might affect their business and to explore potential impacts.

“Firms can hardly begin to understand change until they know what it consists of. Brexit uncertainty for businesses still looms large,” Morgan, who was a supporter of Britain remaining in the EU in the 2016 referendum campaign, said.

Prime Minister Theresa May hopes to clinch a transition deal next month that would keep Britain’s relationship with the EU largely unchanged for around two years after the country leaves the bloc in March 2019.

But there remains little detail on what kind of long-term deal Britain will secure with the EU.

May wants to get as much access as possible to the bloc’s single market for goods and services such as banking. The EU says it will not give Britain that kind of deal without concessions on immigration and the European Court of Justice, that May opposes.

Morgan said without clarity on Brexit, companies would have “no choice but to prepare for the one eventuality that they can understand: the worst-case scenario of a trade relationship based on World Trade Organization commitments.”

The head of a group representing Britain’s insurance industry said his members needed to be clear about the terms of the transition now because contracts spanning the date of Brexit were already being drawn up.

“It is important that when we transition, we know what we’re transitioning to,” Steve White, chief executive of the British Insurance Brokers’ Association, said. “Not knowing what the landscape will be like post-March 2019 means businesses cannot plan and some are already planning for the worst.”