He said the party's annual conference in Birmingham, starting on September 30, could prove a decisive moment as Mrs May is forced to acknowledge the scale of grassroots opposition to her proposals.
Despite the more positive atmosphere surrounding the talks with the EU, UK prime minister Theresa May is facing a renewed threat from inside her own party.
The environment secretary described rumours of a direct leadership challenge "whether it was by Boris (Johnson) or any other individual" as "loose talk" that would distract from the Brexit "mission". But it broke up without a decision on a plan of action. If leaders agree at the September 20 meeting, diplomats expect a final set of guidelines to be formally adopted at the October summit of European Union leaders, setting the stage for a special Brexit summit in November, where the two sides would aim to conclude talks.
Garvin said the jobs of only "hundreds" of JPMorgan's 16,000 staff in the United Kingdom would be immediately affected by Brexit, though that could rise to around 4,000 in the years to come depending on the settlement reached between Britain and the EU.
In a sign the Government remained committed to its plan, he told BBC's Andrew Marr Show: "I think the only deal that we've got on the table, that's the Chequers deal".
The Brexit European Research Group called for the government to agree "equivalence of United Kingdom and EU regulations" for agricultural products in order to keep the border open, and allow Brussels inspectors into Northern Ireland to check their implementation. This is seen as critical by both sides, but talks have been deadlocked for months. "I think it is possible".
He told Newsnight: "If you listen carefully to what Michel Barnier said there was no movement, there was an expression of confidence that we can get an agreement on the withdrawal agreement where we are going to give them £39 billion".
Justin Bieber & Hailey Baldwin Spotted at Marriage License Courthouse in NYC
It was also reported that Justin thanked some of the court officials for keeping their appearance in the courthouse quiet.
Lawmakers from the European Research Group (ERG), a grouping in May's Conservative Party which wants a sharper break with the EU, met on Tuesday night and openly discussed May's future.
May's proposal for a post-Brexit free trade area with the European Union for goods, which would include accepting a "common rulebook" for those goods, have angered committed Brexiteers inside her party. One of those present said opposition to her leadership has hardened over the summer.
BREXITEER proposals to resolve the Irish border issue are "boring" but offer a commonsense solution to the problem, according to Tory MP backers.
Home Secretary Sajid Javid rebuked his former Cabinet colleague, saying "there are much better ways to articulate your differences".
"Brexit is a negative negotiation, unfortunately".
"Any diversion or any distraction from that mission means that our ability to ensure that the referendum mandate that we were given is delivered, is undermined".