In an age when shops and bars routinely open their doors on Sundays to tempt a grateful public away from their religious observances, one London institution has tenaciously resisted consumer demand.

West End theatres are the last places of entertainment in the capital to retain the 1950s ethic of keeping Sunday as a day of rest. Now, tradition is about to be overturned as theatres and actors prepare to strike an historic deal that will provide widespread Sunday performances.

At present only a tiny minority of shows play on Sundays and their producers have to make ad hoc arrangements with Equity, the actors’ union. However, as Sunday leisure habits have diversified in the past 20 years so theatre owners have yearned to tap into the crowds of paying punters flocking to shops, cinemas and football matches on the Sabbath.

The National Theatre introduced Sunday openings last month after striking a separate in-house deal with the unions. Sunday performances are already common on Broadway and in the rest of Europe.

After 16 months of difficult and occasionally fractious negotiations between the Society of London Theatres (Solt) and Equity, a deal is on the table that will increase the minimum Theatreland wage from £416 a week to as much as £600 in return for a number of concessions, including Sunday openings.

For the first time Equity has recommended to its members that they accept Solt’s offer and both parties are hopeful that a deal is in sight, The Stage newspaper reported yesterday.

West End casts are expected to finish voting on the proposals today. If a majority accept it, the four-year deal will introduce a new three-tier pay system into the West End, with a minimum rate of £550 per week for venues with 1,100 seats and above, £500 for those with 800-1,099 seats, and £450 for smaller theatres.

In addition actors and stage management staff who are asked to work Sundays as part of their six-day, eight-performance week will have their pay packet supplemented by an extra £50.

Although a select few star names make good money in the West End, most theatre workers are not very well paid. The majority of Equity’s members have second jobs to supplement often meagre incomes and, according to a survey in 2006, nearly half earn less than £6,000 a year from acting.

Stephen Spence, the union’s assistant general secretary for theatre and variety, told The Stage: “The new deal provides a different way of doing things in the West End and a new framework moving forward. What this deal will do is make it more possible for our people to put bread on the table and milk in the fridge, without relying on the second job. It has been extraordinarily difficult, time-consuming and at times frustrating, but we feel we have got enough now to be able to recommend to members that they do not need to strike.”

Nica Burns, the president of Solt and owner of five West End theatres, said that Equity’s endorsement of the deal was “absolutely brilliant”.

“It’s the 21st century now and this is what people want. There is a big demand for theatre on Sundays.”

Nick Allott, managing director of Cameron Mackintosh Ltd, which owns seven West End theatres, emphasised that there was “not a done deal yet”. However, he welcomed the prospect of Sunday performances, particularly for underperforming shows.

“Sell-out shows won’t necessarily make the move [because of the extra wage costs] as you can’t do better than 100 per cent sales. Big shows with spare capacity will consider it very seriously. This is something we have wanted for a very long time and I’ve been involved in negotiations of one sort or another for at least ten years.”

Nick Hytner, artistic director of the National Theatre, has previously acknowledged that Sunday openings are difficult for staff with families, but said that the theatregoers deserved a better service. “We’ll do our best to make it as painless as possible but we’ve got to do it because we are a public service.”

Changes to Sunday trading practices have always provoked controversy. Sunday trading was legalised officially in 1994 in England and Wales, after 26 previous attempts to relax the law failed because of lobby groups wishing to keep Sunday sacred.