Unlike many of her fellow MPs, there were no public declarations of intent on social media but she has since set out her reasons for supporting Mr Johnson.
Cllr Sean Woodcock, leader of the Labour group on Cherwell District Council, hit out after the result was announced.
He said: "This evening Victoria Prentis, our MP, showed that she is on the side of lies and law-breaking.
"He then lied to parliament again and again about it. An insult to our democracy and to the bereaved and heartbroken who abided by the rules he set.
“Victoria Prentis has said, repeatedly, that she understands the hurt and is sorry.
“But these are crocodile tears. By siding with the lying lawbreaker in No. 10, she has shown whose side she is on. And it isn't the people of Banbury and Bicester.
And looking ahead to whenever the next general election may be, Cllr Woodcock added: “We won't let her, or her electorate, forget it."
But Mrs Prentis released a statement, today, Tuesday: “Last night, I voted for the Prime Minister in the vote of confidence.
“Now that we have the result, it is time to focus our efforts on delivering on what we were elected to do. I remain committed to serving my constituents and focusing on my Ministerial responsibilities at Defra.
“The past two years have seen an unprecedented period of global upheaval, with the deadliest pandemic in a century and now war on European soil which has led to surging inflation and rising costs. I continue to support the Prime Minister as we endeavour to lead the international response to the collective issues we face.
“We are all very concerned about the cost of living. In my ministerial role, my immediate focus is on tackling food security at this difficult time. We are working across government and with our international partners to ensure that food continues to reach those who need it most.”