A source in Brussels familiar with the correspondence said the letter questioned the link between European directives and G20 initiatives, the cost-benefit analysis of certain regulations and the level consultation with industry over the new rules.

The source said Barnier had responded to the letter, though the Treasury Select Committee has not yet fully considered his response and therefore declined to reveal the contents of either letter. The correspondence is set to be published shortly.

The December evidence session included a number of exchanges between committee members and the Commissioner, with Tyrie in particular taking a hard line of questioning.

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