Tom Watson is to issue a rallying cry to dispirited Labour centrists, calling on his party not to fail Britain at a “great moment of change”.

In a speech on Saturday likely to be read as a thinly veiled challenge to Jeremy Corbyn, the deputy leader will say: “The country needs the leadership that only we can give. Let’s make sure we do not fail them.”

Watson, whose post is directly elected by the Labour membership, is more sympathetic to the idea of a second Brexit referendum than some of his shadow cabinet colleagues.

As Corbyn faces the challenge of navigating through another tumultuous week at Westminster, with MPs due to vote on alternatives to Theresa May’s Brexit plan, Watson will say his party has a duty to “engage intelligently” with the government. “But the prime minister must create the conditions for that engagement. And I fear her inflexibility and lack of imagination will mean she is unable to do so,” he will tell the Fabian conference on Brexit in London.

Corbyn declined to meet May unless she first ruled out the option of a no-deal Brexit. He will table an early day motion in parliament on Monday calling on the government to rule out leaving the EU without a deal. EDMs have no formal effect and are not usually signed by frontbenchers, but Labour hopes to attract the backing of MPs from all parties to underline the strength of feeling about the issue.

The shadow Brexit secretary, Keir Starmer, will speak at the same conference as Watson, and call for parliament to have an “open and frank debate” about how to break the Brexit deadlock.

Without criticising Corbyn directly, Watson will call for Labour to reach out to those who have voted for other parties, rather than only targeting its traditional supporters.

“We cannot rest on the manifesto for the last election and hope it will deliver victory for us in the next,” he will say. “We must turn our vision to rebuild Britain for the many, not the few into a programme that will deliver both within and beyond our traditional Labour base.”

He will call for the party to face up to rapid changes in society and the economy, such as climate change and automation. “In 1997 the promise of New Labour, New Britain showed how a changed and modern Labour party could change our country. That is the task: to look to the future,” he will say.

In contrast to Corbyn’s approach to foreign policy, he will say Labour’s role should be to uphold the fraying international system. “Our country is at a crossroads. As we leave the EU, our international position will change. We must ensure that this is not a retreat.”

Corbyn and his close allies are sceptical about Britain’s past role in what they regard as the US-dominated world order. But Watson will say that “the history of the Labour party is entwined with the history of this international order, not, as some believe, opposed to it”.

“We can once again be a proud figure on the world stage,” he will say, citing the legacy of his “great political hero” Ernest Bevin. “A partnership of patriotism with internationalism: those are the values of this movement.”

Bevin, a former trade unionist who rose to be foreign secretary, supported the development of a British nuclear bomb, famously saying: “We’ve got to have the bloody union jack flying on top of it”. Corbyn, by contrast, was a long-serving chair of the unilateralist Stop the War coalition.

Some of Corbyn’s team have long been wary of Watson, regarding him as a potential prime mover behind a long-mooted split, which would see centrist MPs break away to form a new party. However, this speech appears to be aimed at persuading Labour colleagues to stay and fight.

A plan to clip Watson’s wings by electing a second, female deputy was abandoned at the last minute at the party’s conference last year, amid fears that it would create a power base for potential leadership rivals, such as Angela Rayner or Emily Thornberry.

Corbyn faces conflicting pressures on Brexit, with the membership and scores of MPs overwhelmingly against it, while others, including many frontbenchers, are nervous about the risk that another referendum would alienate Labour leave voters.

The Conservative MP Sarah Wollaston has said she will table a “People’s Vote” amendment to the government’s plan B Brexit motion after it is published on Monday.

Labour will have to decide how to whip MPs on the question when it comes to the vote on 29 January. The Guardian understands that it has not ruled out abstaining, or offering a free vote, in order to paper over the divisions in the party.