groundless

"But all these claims are groundless and without proof."

The corporation, incidentally, said "these continuing attacks on BBC journalism are completely groundless – it is simply false to say that we give any political party any less scrutiny than any other".

Lot of reasons for that, it’s not groundless optimism.

The Chinese embassy in London called the report "groundless and absurd", adding that China respects freedom of speech in the UK and elsewhere.

Israel has rejected her report as "groundless", saying it would "join the dustbin of history".