Boris Johnson announced on Tuesday that a public inquiry into the UK government’s handling of the coronavirus pandemic would be held within the next year, the first time he has put a date on the investigation.

The prime minister has previously merely said “there will be a time when we must learn the lessons of what has happened” in the government’s efforts to beat Covid-19.

Responding to a question from Sir Ed Davey, leader of the Liberal Democrats, about when an inquiry would be held, Johnson said: “I can certainly say that we will do that within this session. It’s essential that we have a full, proper public inquiry into the Covid pandemic.”

Each parliamentary session lasts approximately a year by convention, which would mean the inquiry will launch before May 2022. Government insiders confirmed that timetable, but did not offer any further details on the form of the inquiry or who would lead it.

Some of the themes covered in the inquiry may include the introduction of nationwide lockdowns in March and November last year; the preparedness of the NHS; procurement of vital equipment; the effectiveness of the Test and Trace system; and whether borders should have been closed sooner.

Holding the inquiry is seen within government as the key moment when it hopes to draw a line under the pandemic. One participant who will be keenly watched will be Dominic Cummings, Johnson’s estranged former chief adviser, who was closely involved with the pandemic response and has been increasingly critical of the PM since leaving government in November.

Cummings will give evidence at a House of Commons select committee hearing on the government’s handling of the pandemic on May 26. He has said he is eager to ensure MPs understand “what and why things went so catastrophically wrong”. He added that it was crucial to hear from “all those in the room for key decisions. Learning from disaster needs extreme transparency.”

Cummings is expected to criticise Johnson for failing to introduce lockdowns more rapidly in March and November, hesitation that some scientists believe was responsible for thousands of excess deaths.

Angela Rayner MP, Labour’s deputy leader, said the inquiry must be “open and truly independent” and should not appear to be “an exercise in the government marking its own homework”.

“We went into this pandemic with the foundations of our public services and our communities weakened by a decade of Conservative governments. We must learn lessons from that, as well as from how the crisis has been handled,” she said.

The Covid-19 Bereaved Families for Justice UK campaign group has urged Johnson to hold an inquiry since the summer of 2020. Jo Goodman, founder of the group, said the inquiry should begin this summer.

“The prime minister may feel he can wait for answers, but bereaved families certainly can’t. Learning lessons from the pandemic is critical to saving lives now and in the future.”

Goodman also said that the inquiry should be on a statutory footing. “Anything less would mean that no one would be compelled to give evidence under oath,” she added.