The offence can be punished with fines of up to £500.
Labour council chiefs say Downing Street officials threatened to withhold cash from areas that refused toughest Covid curbs.
Liverpool mayor brands variations between regions under the same lockdown rules an "inconsistent mess".
It is the second region of England to enter the highest level of restrictions, after Liverpool.
String of geography failures as Whitehall forgets where Warrington is, misses out half of Lancashire, and spells Middlesbrough wrong.
Around one fifth of the UK will be under local lockdown after measures were announced.
Ali Athar Sabbir, 16, and Muhammad Azhar Shabbir, 18, have been missing since Saturday evening.
Order already applies to Greater Manchester, other parts of Lancashire and West Yorkshire, as well as Leicester.
Greater Manchester, parts of East Lancashire and parts of West Yorkshire are all affected.
They were rescued from Gordon Working Men’s Club but died a short time later.