Prime minister Boris Johnson plans to prorogue parliament this month, hoping to bring MPs back to the House of Commons just over two weeks before Brexit.
The Queen agreed to shut parliament – as is convention for the monarchy – causing outrage among those who are concerned about a no-deal Brexit on October 31.
Organisers of the Stop the Coup action are calling the protest for tomorrow at 6.15pm in Guildhall Square.
The event follows protests across the country, with thousands of people campaigning in London, Manchester and Birmingham.
Conservative MPs have been warned if they vote against a no-deal Brexit in Westminster tomorrow, they could be stripped of party membership and forced to stand as an independent.
Gosport MP Caroline Dinenage previously said a no-deal Brexit would be 'neither ideal nor desirable’.
‘Prorogation is both entirely in line with convention and necessary for a new prime minister to introduce much needed legislation on things like crime, adult social care and improving our NHS,’ she said.
‘I dearly want the prime minister to succeed in negotiating a Brexit deal that can pass through parliament. However, taking no deal off the table would fatally undermine his negotiating hand at this crucial point.
‘I will not be voting with those whose real aim is to block Brexit for which two thirds of my constituents voted.’
Labour MP for Portsmouth South, Stephen Morgan, said he will ‘not stand idly by’.
He said: ‘By proroguing parliament, Mr Johnson has not only shown complete disregard for the catastrophic consequences that a no-deal would have for Portsmouth, he has shamelessly stripped away the voice of the people.
‘No-deal threatens working conditions, our public services, and our environment. Whichever way people voted, to leave or remain, no-one voted for Boris Johnson and his Conservative government’s anti-democratic approach to Brexit.’
Thousands of people have signed a petition calling for Mr Johnson to not suspend parliament unless the Brexit deadline is extended or the withdrawal is cancelled.
It was signed by 1,399 people in Portsmouth North, 2,890 in Portsmouth South, 1,362 in Gosport, 1,609 in Havant; 2,175 in Fareham, and 2,203 in Meon Valley.