Experts, activists and celebrities have spoken out in support of The Independent on Sunday's mental health campaign.

The actress Stephanie Cole, who has suffered from severe depression herself and has a schizophrenic younger brother, said: "I can't tell you how important campaigns like this are. It's quite wonderful for people who are sufferers and carers, because we've been ignored for years and years."

Ms Cole, 60, who has been a patron of the charity Rethink for more than 12 years, went on to criticise the new Mental Health Bill as "draconian", "inhuman" and "ill thought out". The actress, who has starred in a number of popular TV series including Waiting for God, Tenko and Keeping Mum, was particularly incensed at the Bill's clause to allow the indefinite detention of people with personality disorders.

"We are talking about the incarceration of people who haven't done anything," she said. "It's like saying that, if you've got cancer, you have to go to hospital for the rest of your life.

"It seems to me that they're shoving this Bill through because it's much cheaper than putting more money into mental health services and caring for people properly. You can see it a mile off.

"These people are ill. They need the help and care they deserve."

Her views were echoed by fellow mental health campaigner and agony aunt Claire Rayner. "A lot of these problems are a result of the measly nature of the Government," said Ms Rayner. "They haven't agreed to do what they need to, which is to build more secure units. It's a disgrace that so many mentally ill people are in prison, and that's where this Government is failing.

"There is a lot of ignorance about mental health.The general image, fostered by papers like The Daily Mail – may it rot – is of extreme cases such as the murder of Jonathan Zito. It's wicked. So much of what happens is not these people's fault. They should be given asylum and protection from themselves."

The author A S Byatt described it as "a tragedy" that so many people were being kept in high-security hospitals unnecessarily.

"The mental health service is seriously underfunded," she said. "This issue should have a place of priority."

The actress Emily Mortimer, 30, who has starred in The 51st State and Love's Labour's Lost, also called for a serious rethink of mental health services in this country.

"I've got friends who have had mental health problems and they've been well treated, but I do think the system needs reforming," she said. "People in this position are already at rock bottom and all we seem to do is kick them down even further."

Marjorie Wallace, founder and chief executive of the charity Sane, which celebrated its 16th birthday last week, criticised consecutive governments' false promises on mental health.

"There have been many cosy pledges, but the evidence for this revolution in mental health services lies way behind the dream," she said.

"There are still desperate people falling between all the Government's promises and strategies. We haven't made good on decades of under-nourishment within mental health services. We've lost 50,000 beds over 20 years, and replaced them with postcode-rationed care in the community."

Rebecca Fitzpatrick, a prominent mental health and human rights lawyer who has been working in the field for eight years, also attacked a number of flaws in the Government's proposed Bill.

"I am very concerned with some of the proposals," she said. "I wonder whether some of them are compliant with European law, to be honest. The Government seems to have gone ahead and ignored all the advice it has been given.

"The system will collapse unless they drastically increase funding – they won't be able to afford all the extra tribunals they have promised, for instance.

"The other primary area of concern is the proposal to extend compulsory treatment into the community. I have serious concerns about the logistics of forcibly entering somebody's house and holding them down to administer medication."