The total soared past a million around 5.15pm with a record number of donations – £824,000 topped up with £187,000 in gift aid.
More than 71,000 people have pledged cash to the Samaritans, with donations peaking at a rate of £300 a minute on Wednesday, in honour of Claire who collapsed and died in Birdcage Walk, near St James’s Park, on the final stretch of the 26.2-mile course on Sunday.
The incredible news came as it was revealed that Claire will be buried alongside her brother, Grant, who died aged 25 from a drugs overdose in 2001.
Claire’s mum said: “She was devoted to her brother and we want them to rest in peace together.
The private ceremony will take place at St Andrew’s Church in the village of North Kilworth, Leicestershire, next Wednesday.
Reverend Emma Davies said she believed some mourners may wear red as it was Claire’s favourite colour.
Rev Davies said: “It is a source of comfort that she has touched the hearts of strangers, because of the way that she died trying to help people.
“I understand that red was Claire’s favourite colour so people may wear red.”
Claire’s family said they had been “amazed” and “incredibly moved” by donations made in her memory.
She was taking part in the event to raise money for the Samaritans, an organisation her mother Cilla had volunteered with for more than 20 years.
Donations on Miss Squires’ page on the JustGiving website soared as news of her death spread, increasing the total from just £500 on Sunday.
Claire’s heartbroken father, Paul, said her death “just doesn’t seem real”.
Paul, said his daughter was “fit as a fiddle” and that it was a mystery as to why she had died.
He said: “We are stunned. She was as fit as a fiddle and went to the gym every day.
“We have no idea how it could have happened and can’t believe she’s just gone.
“She had everything to live for and was an absolutely beautiful girl.
“I can’t believe she’ll never come bouncing through our door again — it just doesn’t seem real.
“She loved life and lived life to the full. She was so determined, so caring, and a joy to be around.”
Monday saw the largest number of donations received in a single day on the JustGiving website, with more than 10,000 people donating together at any given time, the group said.
A spokeswoman for the Virgin London Marathon said: “Claire’s family have been incredibly moved by the measure of support and donations from the public, and are amazed by the amount raised so far, which continues to rise.
“These donations are a lasting testament to their beloved daughter and the cause in which she believed so passionately.
“Claire was particularly inspired to run for the Samaritans by her mother’s 24 years of volunteer work for the Samaritans.”
The spokeswoman added: “Although a post mortem has been held further investigations into the cause of death are continuing and the family will not be making any further statements about this at present.”
In a family tribute released on Wednesday Miss Squires was described as “an incredible, inspirational, beautiful and driven person”.
The statement read: “She was loved by so many and is dearly missed by all of us.
“For Claire and the Samaritans, please keep the donations coming. Don’t stop giving, just like her. It’s what she would have wanted.”
Anne-Marie Huby, managing director of JustGiving, said: “The response to Claire Squires’ tragic death on Sunday has been extraordinary. Out of respect for Claire’s memory, we will be donating our fees back to the Samaritans.”
Samaritans’ chief executive Catherine Johnstone said the charity had been “overwhelmed” by the donations and would be speaking to Miss Squires’ family about how the money should be used.
The charity’s annual turnover from individual donations typically totals around £3.8 million a year, a spokesman said.
Overall, with donations from companies and trust funds, its turnover is some £10m each year.
Pals Nicola and Lucy Short appeared on ITV’s This Morning today.
Nicola said: “Claire was fun. When we climbed Mount Kilimanjaro last year she virtually skipped up it.”
Victoria Hauser said: “Claire was larger than life, fun-loving, bubbly, happy, cheerful, kind, giving, thoughtful.
“She was just the most amazing person in the world – the best friend I have ever had.
“She could never be replaced and dozens of people would feel like that – it’s not just me. Once Claire was a friend, she was a friend for life and a very, very good friend.”
Tests to establish why Miss Squires collapsed are expected to take place in the coming days.
She died with the finishing line only one bend away, after 25 miles of the marathon.
Miss Squires is the 11th participant to die since the event began in 1981.