Organisers of a major Labour Day protest in Hong Kong have vowed to press ahead with their march in defiance of a police warning to cancel it because of the coronavirus epidemic.

Bosses at the Confederation of Trade Unions (CTU) insisted the May 1 demonstration could go ahead without breaking the social-distancing laws in place to stop Covid-19’s spread as they called the force’s ban threat “absurd”.

A senior police source said they had asked both the pro-democracy CTU and the pro-Beijing Federation of Trade Unions to withdraw their protest applications, warning they ran the risk of holding illegal events if they took to the streets regardless.

The source said they would also seek legal advice on how to handle possible bids for the June 4 vigil in Victoria Park to mark the anniversary of the Tiananmen Square crackdown in 1989.

The social-distancing rules, which were introduced in late March and now run until at least May 7, include banning public gatherings of more than four people and shutting 11 types of social and entertainment venues such as bars, beauty salons, karaoke bars and fitness centres.

Traditionally, unions and activists from both rival political camps stage rallies on Labour Day to fight for improvements to workers’ rights.

Referring to the CTU and FTU bids to take to the streets on May 1, a police source said: “We have contacted these groups and asked them to withdraw the applications amid the pandemic.

“If they don’t, we will object to their applications next week given the social-distancing regulations. If they insist on taking to the street, they will be responsible for an illegal assembly and violating the new regulations.”

FTU legislator Luk Chung-hung said they had earlier this week decided to drop plans for the Labour Day march because of the epidemic.

The source said they had so far received no applications for the June 4 vigil in Victoria Park. But the force would seek advice from the Department of Justice to see if there were legal grounds for banning any public assembly even if the social-distancing regulations had already expired.

“We need to clarify if the term ‘public safety’ under the Public Order Ordinance also includes public health amid the pandemic,” he said.

Lee Cheuk-yan, general secretary of the confederation, said: “It is absurd that police want to ban our rally even if we can make arrangements to satisfy the social-gathering restrictions. We can ask people to march in groups of four, with each [group] keeping 1.5 metres (4.9 feet) away.

“Labour Day is on May 1 and we are not going to delay the Labour Day march to after May 7 when the social-gathering rules have expired. Something will definitely take place on May 1.”

The organiser of the biggest anti-government demonstrations in Hong Kong, the Civil Human Rights Front, revealed earlier in the week it had applied for its annual July 1 march to mark the city’s 1997 handover to Beijing.

The police source said they would not process the application until nearer the time and its handling would depend on the development of the pandemic.

Figo Chan Ho-wun, vice-convenor of the front, accused police of trying to abuse their power.

“The Public Order Ordinance does not authorise the police to ban a public rally on health grounds. The Basic Law promises Hong Kong people the freedoms of assembly, of procession and of demonstration. A health regulation cannot override the mini-constitution,” he said.

Under the ordinance, the police commissioner may ban any public meeting if he deems “such prohibition to be necessary in the interests of national security or public safety, public order or the protection of the rights and freedoms of others”.

Chan added: “The police role should be to discuss with us and facilitate public assemblies and processions, say, how a rally can proceed despite the social restrictions, but not asking us to cancel it.”

Richard Tsoi Yiu-cheong, of the Hong Kong Alliance in Support of Patriotic Democratic Movements of China, which organises the annual June 4 vigil, said its plan was to hold it as usual. “I hope the police will not use the coronavirus epidemic as an excuse to ban us.”

Tsoi said the alliance would consider filing an application to police around mid-May.