London either has to back up its “groundless” accusations against Moscow following the attack on Sergei Skripal and his daughter or apologize, spokesperson for Russian President Sergey Peskov told reporters, Tass said.

According to him, Britain allegations that Russia is responsible for attack on Skripal and his daughter are “groundless and slanderous.”

"We understand the solidarity of other countries with the UK,” said Peskov adding that sooner or later UK has to back up its accusations or apologize.

As reported earlier,  UK Prime Minister Theresa May accused Russia of being responsible for attack on Sergei Skripal  and his daughter on March 4 and decided to expel 23 Russian diplomats from UK. May has confirmed no ministers or members of the royal family will attend the World Cup in Russia.