Dame Kelly Holmes has urged No10 to boost support for mental health, after it admitted the service faces £7billion in cuts.
And the Olympic legend warned the cost of living crisis is contributing to a timebomb of problems.
Two-time gold medal winner Dame Kelly, who came out as gay in June, said she wants to send a “very clear message to our Government” to increase support.
The 52-year-old added: “We are living through a mental health crisis.
“Millions are struggling, and far too many people cannot get the support they need. And this is rapidly getting worse as the cost of living crisis takes hold, particularly for people on lower incomes.
“Improving mental health must be a national priority.
“It must be at the heart of everything that is said and done. I want to see a commitment from ministers to publish a strategy for mental health as soon as possible.”
Former soldier Dame Kelly, who won gold in the 800m and 1500m races at the 2004 Games in Athens, realised she was gay at 18 after kissing a female comrade. Her family and friends have known since 1997.
Speaking out ahead of World Mental Health Day on Monday, she told how bottling up her feelings left her suffering episodes of self-harm and even considering taking her own life.
The former athlete said she is in a happy relationship and had wanted to “scream” about her sexuality for years but felt unable to speak openly.
Dame Kelly, who is an ambassador for Nuffield Health, also told how she suffered “burnout” last year.
She said: “I was throwing myself into my work at that time because it stopped the constant voice in my head telling me I needed to be honest about who I really was.
“I lived through some of my darkest days alone before I started talking to friends, family members, colleagues, professionals. Talking is so important.
“I think we can go from talking about mental health over the last decade to tackling it over the next.”
One in every four Brits will experience a mental health problem each year. But NHS England may have to cut mental health treatments due to funding shortfalls.
The Mirror looked at the impact of Covid on mental health a year ago, with our HeadStrong: Better Mental Health For All series.
Our poll found one in four people said theirs had suffered and one in 15 had had suicidal thoughts. Yet there is still no minister for care and mental health listed after previous title holder Gillian Keegan left in September.
A new Lancet commission on Monday estimates a billion people globally are living with a mental health condition and face a “double threat” from the illness itself and the consequences of stigma and discrimination.
No10 said: “Mental wellbeing is a priority for the Government and we will invest an additional £2.3billion per year into services by 2024.”
