Mays digital performance was also up 20% year on year.
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Channel 4s record low audience share was echoed in other ratings data.
Its reach stood at 35.8M in May, according to audience body Barb.
‘Gogglebox’Channel 4/Studio Lambert
This was down 1M on April and 3.5M on May last year.
Channel 4 was not alone in experiencing a ratings slump.
Its closest rivals Channel 5 and BBC2 suffered year-on-year reach declines of 2.8M and 1.9M respectively in May.
The figures have exacerbated concerns about Channel 4s reliance on aging brands to bank ratings.
There is also anger that it has not clearly communicated its issues.
Channel 4 said: Channel 4 is well ahead of other broadcasters in its digital transformation.
We would expect this trend to continue over the next few years.
It is ahead of other UK broadcasters with this ambition.
