Philip Hammond has said the government will "get the very best possible deal that we can for Britain", amid concern European leaders will force a "hard Brexit".
Speaking on The Andrew Marr show, Hammond said: "I do understand the frustration among people who would like us to be much more open about what we're thinking of doing and how we're going to conduct negotiations, but look at what the Europeans are doing."
The chancellor wouldn't be drawn on increasing criticism the government has faced over its lack of details on Brexit plans.
He said the Europeans were taking a "very disciplined line, keeping their cards very close to their chest in order to maximise negotiating advantage", and the British government would be doing the same.
"I want to ensure Theresa May goes into these negotiations with all the cards in her hand, with maximum negotiating flexibility, so that she can play her hand to the maximum benefit of Britain," he added. "That's in all our interests, and with the greatest respect, those who are urging us to reveal our tactics are inviting us to undermine our own negotiation."
Hammond stressed that he didn't think it was helpful for the government to go into a negotiation "having unilaterally decided certain things we will or won't do".
The Observer reported that European leaders had come to a 27-nation consensus that a "hard Brexit" will be the only way to clamp down on others following in Britain's footsteps, which could ultimately lead to a break up of the European Union.
Favourable terms for Britain would likely encourage other nations with strong Eurosceptic movements.
A leaked Deloitte memo last week said the government didn't actually have a plan for Brexit, and warned that more than 500 Brexit-related projects were "beyond the capacity and capability" of government.
In response, Downing Street accused the accountancy firm of "touting for business". In a briefing to journalists, the Prime Minister's spokeswoman said the memo which had been obtained by The Times, was an "unsolicited document that has nothing to do with the government at all".