Ministers are “pretty confident” that the final lifting of Covid restrictions in England, delayed until 19 July, will not be pushed back again, Michael Gove has said.

The Cabinet Office minister sought to reassure people the government was trying not to impose “imprisonment” any longer than necessary, after Boris Johnson announced the Delta variant of the coronavirus, first discovered in India, had derailed his roadmap for easing restrictions.

Businesses shut since the start of the pandemic, such as nightclubs, and hospitality firms which complain they cannot operate profitably with social distancing, will have to follow the existing rules for up to a further four weeks. Johnson said this was to offer all adults a first vaccine dose by the point of unlocking and promised a review on 5 July, although No 10 admitted it was unlikely curbs would be dropped at that point.

Gove defended the decision he made along with other senior ministers, including Johnson, the chancellor and health secretary, over the weekend, to remove the cap on attendance at weddings.

Asked if Johnson was guaranteeing step four of the roadmap would go ahead on 19 July, given he had described it as a “terminus date”, Gove told BBC Radio 4’s Today programme he was “pretty confident” there would be no need for further delay.

“None of us can predict with perfect foresight the circulation rate or potential new variants,” he said, stressing that ministers were confident the current vaccines provide the “highest level of protection, come what may”.

Gove added the delay would take England up to the start of the school holidays, which should cut transmission further, though he added: “We are going to have to live with Covid.”

Speaking to LBC, Gove said only a “bizarre, unprecedented event” could lead Johnson to push back the 19 July unlocking even further.

He also dismissed calls the government should have acted faster to put India on the red list by restricting travel from it at the same time as Bangladesh.

“You can only take a decision based on the evidence you’ve got at the time,” Gove said. “So we can all look back and think ‘hmm, if only?’ but we took the decision to put India on the red list before the Delta variant was a variant under investigation, before it was designated as a variant of concern.”

However, he was warned by a member of the government’s Scientific Advisory Group for Emergencies (Sage) that the number of Covid-related deaths could easily rise to hundreds a day again.

Prof Graham Medley told BBC Radio 4’s Today programme: “Although the numbers of deaths are low at the moment, everyone expects that they will rise. The question is really as to what level they will rise.”

Asked if the country could see hundreds of fatalities a day, he said: “Oh easily. I think we still might at some point.”

Some restless Conservative MPs think it was wrong for the government to delay the easing meant to take place next Monday, on 21 June.

Mark Harper, the chair of the Covid Recovery Group and a former minister, told LBC: “We could have moved ahead perfectly safely on the 21st of June.”

He said Johnson’s optimistic comments about 19 July “are exactly the same words as he was using about 21 June, so some of us, I’m afraid, are a bit worried that we’re not going to actually move forward on the 19th of July”.

He continued: “Ultimately we’ve reduced the risk of this disease hugely by our fantastic vaccination programme, and, as the government says, we’ve got to learn to live with it, but the problem is every time we get to that point, ministers seem to not actually want to live with it and keep restrictions in place.”