A mother accused of murdering her three-year-old daughter has told a court she deliberately drowned the girl because she believed she was “safer in heaven” than with her estranged husband.

Claire Colebourn, a former biology teacher, claimed her husband, Michael, a chief executive, “hammered” her emotionally and would not let her and their daughter Bethan “be at peace”.

Colebourn, 36, told a jury at Winchester crown court she thought the only way to keep her daughter safe was to kill her and ensure she could not be anywhere near her father.

After drowning Bethan, Colebourn, who has diabetes, tried to kill herself by injecting a large dose of insulin, hanging herself and stabbing herself in the stomach, the court has heard.

Giving evidence, Colebourn told jurors: “When your emotions are being hammered by somebody so much and you see your beautiful little girl suffering as well because she feels for her mummy.

“She’s going to be a lot safer in heaven than she is anywhere near her father. The spirit can be at peace then, and Michael would not let us be in peace.

“As a mummy who loved her daughter, and still loves her daughter, so much, to have your little girl telling you she doesn’t want to see her own dad – I don’t think any mum could deal with that. I would walk to the end of the earth for her.”

When asked by the prosecuting barrister, Kerry Maylin, what she had intended to do to Bethan in the bath, Colebourn, who denies murder, said: “I can’t use the words you want me to. She was going to be safe, because she would be in heaven. Bethan was going to pass into heaven. I was in an emotional state.

“I didn’t think I was going to be here today saying this, I thought I was going to be with Bethan in heaven. I have no idea how I am still alive. It’s been very hard, because I have been forced to stay alive.”

Colebourn allegedly murdered Bethan at their home in Fordingbridge, Hampshire, in October 2017. The prosecution alleges Colebourn murdered her daughter because she wrongly believed her husband was having an affair. Bethan’s body was found the next day in a downstairs bed, her hair still wet, the jury has heard.

In the days before the alleged murder, Colebourn researched drowning on the internet and looked for information on churches and cemeteries, the jury has heard.

Earlier Colebourn cried in the dock as jurors were read a police interview in which she allegedly made a full confession.

She told officers she thought it was best that Bethan died, explaining: “I didn’t want her to be in pain.”

In the interview, Colebourn allegedly said: “I can’t be a liar, I can’t do it – Bethan drowned. I am going to have to go against legal advice.

“Bethan drowned and I am responsible for her death. I was there, I held her under the water. Why did I do that? Because I didn’t want her to go anywhere near her father. Whether that was right or wrong, that is desperate times for you.”

Colebourn allegedly said Bethan told her she did not want a bath. “She went to the bathroom, saw the bath running and just said: ‘I don’t want a bath mummy, I don’t want a bath’.

“I have never been so stressed in my life. Then I drowned my daughter, I drowned my own daughter. It’s going to haunt me for the rest of my life. Her whole body jumped after holding her for a while.

“She didn’t fight against my hand. Her arms were tucked under her. I think sadly, very sadly for her now. She had complete and utter trust in me, didn’t she?”

The trial continues.