British retailers have brought forward their Christmas clearance sales online in the hope that shoppers will log on to buy bargains and offset lacklustre spending in stores.

Marks & Spencer launched its sale online at midday on Monday, it said on its website, while department store John Lewis said it would cut online prices when its stores close at 5pm yesterday. Debenhams has already started its online sale.

Retailers in recent years have started sales online on Christmas Day, ahead of the clearances in stores from Boxing Day, but are increasingly launching their online offers before Christmas after delivery deadlines for the day have passed.

Hard-pressed shoppers have been leaving it later to buy presents in the hope that retailers would slash prices, the British Retail Consortium said.

It was forecasting that £5 billion would be spent in the shops on Saturday and Sunday combined, the last weekend before Christmas.

Richard Dodd, the BRC’s head of Media and Campaigns, said weekend trading had met expectations.

“Christmas, ultimately once all the final sums are done, will turn out to be acceptable but not exceptional,” he said.

He said the sector expected a modest increase in cash spending against a year ago, but not necessarily any significant increase in real terms once inflation was stripped out.

Many British families’ budgets are stretched, according to a survey from Markit that showed the biggest deterioration in household finances for seven months.

Analyst Howard Archer at IHS Global Insight said the weakening in household finances could not come at a worse time for retailers, and it highlighted why many people appeared to have been careful in their Christmas shopping this year.

“The suspicion has to be that consumers will be especially keen to take advantage of genuine major bargains in the sales to acquire items that they cannot otherwise afford or are reluctant to make at the moment,” he said.

“However, we suspect that people will likely to be more careful in buying – or reluctant to buy – items that they don’t really want or need in the sales.”