LONDON (Reuters) -Britain faces a "tidal wave" of the Omicron variant of coronavirus and two vaccine doses will not be enough to contain it, Prime Minister Boris Johnson said on Sunday, as he accelerated the booster rollout programme.

       Speaking hours after government scientists lifted the COVID alert level to 4 on a 5-point scale, Johnson said the booster programme must go faster because scientists did not yet know if Omicron was less severe than other variants.

       "A tidal wave of Omicron is coming," Johnson said in televised statement on Sunday evening. "And I'm afraid it is now clear that two doses of vaccine are simply not enough to give the level of protection we all need."

       He added that scientists knew Omicron was much more transmissible and that a wave of the variant through a population that was not boosted would result in so many hospitalisations the National Health Service would struggle to cope.

       "Everyone eligible aged 18 and over in England will have the chance to get their booster before the New Year," he said.

       (Reporting by Andy Bruce; Editing by Kate Holton)