Data from the national coronavirus infection survey shows that 38 per cent of cases in the region for the week starting December 21 were the new mutant strain compared with 11 per cent for the week beginning December 9.
This is compared to the new strain being identified in 77 per cent of cases in London and 72 per cent of cases in the South East for the most recent period.
It comes after the Black Country, Staffordshire and Birmingham were all placed into Tier 4 along with London, the South East and other areas. Meanwhile Shropshire and Telford & Wrekin were moved up to Tier 3.
Walsall Council leader Councillor Mike Bird said said the increase was "very worrying" and stressed the focus needs to be on rolling out the vaccine – and protecting vulnerable people against the virus.
Councillor Bird said the "good news" is that the vaccines – both the Oxford AstraZeneca and the Pfizer-BioNTech – seemed as effective against the mutant as it is against the regular strain.
He added: "It's very worrying about out the increase of cases involving this new strain which seems to be more contagious. But people need to understand the basics of 'Hands, Face, Space' and be vigilant."
Health chiefs in the region are already expecting a further surge in the new variant over the next few weeks.
Clive Wright, the Covid-19 regional convener for the West Midlands, said at a briefing on Thursday: "Overall, the cases of coronavirus are increasing across the country. There's a new variant of the virus which is much more contagious and so it has spread very quickly, although the illness caused by the new variant is no more severe than the previous variation of the virus.
"So far the South East, East and London have been the most impacted and we've seen cases rise to over 1,500 per 100,000 of population. This is putting an extreme pressure on NHS services in those regions.
"In the West Midlands, overall, the levels of coronavirus are increasing but at a much slower rate than other parts of the country that I've mentioned.
"This would indicate that levels of the new variant virus are lower in the West Midlands, but it's likely that this will change and we may now see a surge over the next few weeks."
Figures by region:
For the week beginning December 21.
Cases of the new mutant strain, as a percentage of overall coronavirus cases, according to analysis of ONS figures.
- London: 77 per cent
- East: 76 per cent
- South East: 72 per cent
- North East: 47 per cent
- West Midlands: 38 per cent
- North West: 32 per cent
- South West: 30 per cent
- East Midlands: 29 per cent
- Yorks Humber: 25 per cent
- England: 63 per cent
Boris Johnson has said the new variant could be up to 70 per cent more transmissable than the original Covid-19 strain, and countries across Europe have banned people from travelling from the UK as a result.
The strain was first identified in October, from a sample taken in September, but it was not until December that its higher transmissibility was confirmed.
Seven per cent of cases in the West Midlands were the new strain in the week starting November 18, 10 per cent were in the following week, then 13 per cent in the week from December 2 and 11 per cent in the week beginning December 9.
In the same period the proportion of cases caused by the new strain went from 28 to 62 per cent in London and 15 to 28 per cent in Wales.