The change in strategy from Change UK's spokesperson comes after multiple polls showed the newly-formed party struggling to gain ground in the polls ahead of this week's European elections.
In what appeared to be an attempt to distinguish the party from other pro-European groups, the ex-Labour MP said: "I have come to the view that we are now at the point where we are going to need to revoke Article 50."
Speaking to the BBC's Andrew Marr Show, Mr Umunna continued: "The way to resolve this impasse is to refer it back to the people. The simple fact right now is we do not have time do a People's Vote before 31 October."
"What would be undemocratic is to impose a no-deal Brexit on this country which there is not a mandate for. All the polls show the majority of people want to remain in the European Union.
"We are faced with a national emergency. No deal is facing us in the face and we have got to deal with it," he said.
According to two separate polls published on Saturday ahead of the Euro elections on Thursday, Change UK received just four and three per cent of the vote share, while Vince Cable's Liberal Democrats surged ahead on 15 per cent and the Greens had the backing of 11 per cent of those polled.
Asked whether he believed his party had been competent since its creation, Mr Umunna continued: "I do, but look we're a four week old party. We only left the Labour Party three months' ago. It's a complete start-up - we're the youngest kid on the block in this election."
The remarks came after Rachel Johnson - a candidate for Change UK in the European elections - criticised her party in an interview with The Times.
Ms Johnson, the sister of the ex-foreign secretary Boris, said the party's name was "terrible", adding: "They want to focus-group everything and they have a leadership team of about 11 people.
"If I were running it we would have one leader and a different name and we would have done a deal with all the other Remain parties. Then we would be able to give the Brexit Party a fight."
But Mr Umunna insisted it was a "joke", adding: "It was taken out of context".