LONDON: Dominic Cummings, British Prime Minister Boris Johnson's controversial former top aide and architect of Brexit, is set to take aim at the government Wednesday during a marathon grilling from lawmakers.

Cummings, who stepped down as Johnson's chief adviser in December, has launched a series of explosive attacks in recent weeks against his former boss's coronavirus policies and financial dealings.

A divisive figure who carved out a uniquely powerful role during the first 18 months of Johnson's government, he has accused the UK leader of lacking competence and integrity and his government of "appalling ethics".

Cummings has previewed his expected testimony ahead of his much-anticipated appearance in front of a parliamentary committee scrutinising the government's pandemic handling, which is scheduled to begin at 9:30 am (0830 GMT).

In dozens of social media posts, he claimed Johnson had adopted a haphazard approach, initially favouring a so-called herd immunity strategy before belatedly abandoning it when the likely death toll became clear.

If Britain had had "the right preparations + competent people in charge", it could probably have avoided its first lockdown in March 2020 and "definitely" escaped later ones, Cummings wrote, as part of a 59-message Twitter thread.

"Given the plan was AWOL/disaster + awful decisions delayed everything, lockdown1 became necessary."

He also accused Health Secretary Matt Hancock of lying about the government's true plans.

Downing Street has denied ever pursuing a herd immunity strategy.