Betting firms must check in with online gamblers after an hour to try to protect vulnerable people during the coronavirus pandemic, the Gambling Commission has said.
The closure of sports venues and events has led to a drop in gambling overall.
However, the watchdog said there had been a shift to online products such as poker and virtual sports.
And some gamblers may be at greater risk of harm in the lockdown, the Gambling Commission said.
The advice to contact customers after an hour of play is part of new guidelines released by the watchdog.
They are designed to protect people from getting into financial difficulties from gambling.
The Gambling Commission's chief executive Neil McArthur said: "Operators must use the data they hold to protect their customers and now, more than ever, it's vital that online operators really know their customers by monitoring how long they are playing for and understanding how financial uncertainty is impacting them and what they can afford to gamble with."
Previously, gambling firms had to interact with online customers after an unspecified amount of time, to check whether they were at risk of harm.
This would be in the form of a web chat or a phone call which could then result in the customer being excluded from play.
That time limit will now be an hour for the duration of the lockdown. Although, the commission said the measure could become permanent following a consultation on the guidelines with the gambling industry.
The new guidelines include the prevention of so-called "reverse withdrawal" which is when customers withdrawing their winnings decide instead to use the funds to bet with.
Gambling firms also need to reassess the indicators they use that flag up when a customer could be at risk of harm.
Firms are already supposed to do affordability assessments for new customers if they pass a threshold, say by spending £100 on three consecutive days.
An affordability assessment could be asking a customer to provide payslips, for example.
Similarly, they should reassess when to offer bonuses and promotions to gamblers, and they should continually monitor customers, looking at how their patterns of play and spending have changed in recent weeks.
Commission data shows that overall, gambling is down during the lockdown due to the closure of betting shops and the cancellation of sports events.
However, there has been an increase in some gambling, including online slots, poker, casino gaming and virtual sports.
The majority of people who gamble have not started spending more time or money on betting.
However, 8% of those people who gamble are what the Commission defines as "engaged gamblers" - that is, people who have used three or more gambling products in the last four weeks.
And two thirds of those "engaged gamblers" have increased the time or money they are spending on at least one online gambling activity.