Michael Gove has made a pitch to be in Boris Johnson’s cabinet regardless of whether it pursues a no-deal Brexit and has lavished praise on his former bitter rival who stands on the brink of becoming prime minister.

Gove set out his view that Johnson and Jeremy Hunt would be “great prime ministers” and claimed “we can trust them both to do the right thing on every critical issue”. His attempt to bury the hatchet with Johnson, who is likely to enter No 10 next week, comes three years after Gove sank his former friend’s last leadership bid with a stinging character attack.

Speaking at Kew Gardens, the environment secretary would not say which of his former leadership rivals he would vote for in the contest but claimed to have deep admiration for them both after watching them in cabinet.

“I won’t say who I’m going to vote for. It will be the love that dare not speak its name,” he said, dismissing his previous criticism of Johnson as unfit to be prime minister as “based on events at that time”.

Q&A What does a no-deal or WTO-rules Brexit mean? Show If the UK leaves the EU without a deal it would by default, become a “third country”, with no overarching post-Brexit plan in place and no transition period. The UK would no longer be paying into the EU budget, nor would it hand over the £39bn divorce payment. The UK would drop out of countless arrangements, pacts and treaties, covering everything from tariffs to the movement of people, foodstuffs, other goods and data, to numerous specific deals on things such as aviation, and policing and security. Without an overall withdrawal agreement each element would need to be agreed. In the immediate aftermath, without a deal the UK would trade with the EU on the default terms of the World Trade Organization (WTO), including tariffs on agricultural goods. The UK government has already indicated that it will set low or no tariffs on goods coming into the country. This would lower the price of imports – making it harder for British manufacturers to compete with foreign goods. If the UK sets the tariffs to zero on goods coming in from the EU, under WTO “most favoured nation” rules it must also offer the same zero tariffs to other countries.

WTO rules only cover goods – they do not apply to financial services, a significant part of the UK’s economy. Trading under WTO rules will also require border checks, which could cause delays at ports, and a severe challenge to the peace process in Ireland without alternative arrangements in place to avoid a hard border.

Some no-deal supporters have claimed that the UK can use article XXIV of the General Agreement on Tariffs and Trade (Gatt) to force the EU to accept a period of up to 10 years where there are no tariffs while a free trade agreement is negotiated. However, the UK cannot invoke article XXIV unilaterally – the EU would have to agree to it. In previous cases where the article has been used, the two sides had a deal in place, and it has never been used to replicate something of the scale and complexity of the EU and the UK’s trading relationship. The director general of the WTO, Roberto Azevêdo, has told Prospect magazine that “in simple factual terms in this scenario, you could expect to see the application of tariffs between the UK and EU where currently there are none”. Until some agreements are in place, a no-deal scenario will place extra overheads on UK businesses – eg the current government advice is that all drivers, including lorries and commercial vehicles, will require extra documentation to be able to drive in Europeif there is no deal. Those arguing for a “managed” no deal envisage that a range of smaller, sector-by-sector, bilateral agreements could be quickly put into place as mutual self-interest between the UK and EU to avoid introducing or to rapidly remove this kind of bureaucracy. Martin Belam

He described Johnson as having been “passionate about the environment for decades”, claiming that when they first met “he described himself to me without prompting as a passionately green Tory and in every role he has had he has championed the environment”.

Labour has called Johnson’s commitment to tackling the climate emergency into question, pointing out that he denied climate science as recently as 2015 when he described it as “without foundation”.

Pressed on whether he would serve in the cabinet of Johnson, who is willing to carry out a no-deal Brexit on 31 October, Gove said: “Whoever is the prime minister, if they wanted me to serve in their government I would be happy to do so. If they wanted to send me to the backbenches I would completely understand.”

Gove said the Brexit plans of both men had “much to recommend” them, a day after Johnson and Hunt hardened their positions on leaving the EU, with the candidates labelling the Northern Ireland backstop “dead” and rejecting the idea of simply adding a time limit or exit clause.

Amber Rudd, the work and pensions secretary, took a different stance on Tuesday, warning that both Johnson and Hunt were on course to “collide with reality” over their Brexit plans. Rudd, a Hunt supporter, has said she would be happy to serve in the cabinet of either man and has backed down on her campaign against a no-deal Brexit.

But she told a Politico event that neither candidate appeared to be thinking realistically with their plans to strike a new deal without the Northern Ireland backstop, adding: “I think they will find they have to compromise.”

Gove initially gave a speech, lasting more than 30 minutes, setting out his view of his achievements as environment secretary, and said the government would back signing up to international air-pollution targets set by the World Health Organization (WHO).

“Our environment bill is being drafted to include a legally binding commitment on particulate matter so that no part of the country exceeds the levels recommended by the WHO,” he said, without saying by what date that target would be reached.

Michael Gove and Boris Johnson (right) pull pints at the Old Chapel pub in Darwen, Lancashire, during the Vote Leave campaign in 2016. Photograph: Stefan Rousseau/PA

But asked if he wanted to stay on in the department, Gove did not make a special plea to remain as environment secretary, saying he had merely been giving in the speech a “personal indication of the way which I would hope policy to develop, whoever does this job”.

After setting out his stall as a reforming cabinet minister, he added: “It is an amazing, wonderful job and I wish whoever does it in the future nothing but good fortune. This speech is designed to ensure there is a solid platform whoever continues to do this job.”

His remarks are likely to fuel speculation that Gove will be pressing Johnson for a new brief in a department with pressing problems, such as housing or transport.

Johnson is adamant that he has not been offering jobs to anyone before entering No 10, as appears likely to happen next Tuesday. He has even declined to say that Hunt will be allowed to stay in the cabinet. It remains to be seen whether he will forgive Gove for his betrayal in 2016, although senior Eurosceptics believe he will extend the hand of friendship with a cabinet post.