Events sector leaders said the industry has "been hung out to dry" after plans to restart conferences, exhibitions and large sporting events on 1 October were put on hold.
Prime minister Boris Johnson confirmed today that from Monday a maximum of 15 people, instead of 30, would be able to attend wedding ceremonies and receptions. Funerals will remain at a maximum of 30 people.
The tighter restrictions are part of a move to "tighten up the rule of six" and come after the coronavirus alert level was upgraded on Monday from 3 to 4.
In a further blow to the sector, Johnson also confirmed that business conferences, exhibitions and large sporting events would not be able to reopen on 1 October despite a small number of sporting pilot events, designed to test the safe return of spectators, having been held.
Alex Head, founder of London-based events caterer Social Pantry, said that the new measures were "definitely a challenge".
She told The Caterer: "The main problem is on the events side, there have been no grants, no rent relief. The rule of six blew everything out of the water. I've already lost two-thirds of the workforce. Teams are already smaller and have adapted.
"Where we had 100 staff, we have 23 left now. What more can you do? It will lead to more redundancies."
She said it was vital that insurance companies paid out and called for sector-specific care packages to be introduced.
The Meetings Industry Association (MIA) has responded to the latest restrictions by saying it will continue "its fight for support for the business meetings and events industry".
Chief executive Jane Longhurst said: "We already know that venues have averaged a £2,398,600 loss of business to date, but unlike other sectors, business meetings and events has only received the basic package of support.
"This is revenue that simply cannot be borne any longer. Venues will be closing; more jobs will be lost. We need financial support as quickly as possible.
"Without a clear re-opening date and no clear idea if there is going to be any support forthcoming, this industry has simply been hung out to dry."
Johnson has also brought in tighter penalties for those who "brazenly" defy the rules, with fines of up to £10,000 applied to businesses who fail to comply and promised to provide the police and local authorities with "the extra funding they need" and a greater police presence on the streets.
The news comes after the reopening of events in England was given the go-ahead from 15 August, after the initial lifting of restrictions planned for 1 August were postponed.