Jess Phillips has vowed to speak “plainly” as she prepares to make her pitch to members in the upcoming Labour leadership hustings.
The five candidates in the race to succeed Jeremy Corbyn will descend on Liverpool on Saturday to mark the start of their hustings tour around the UK.
Ms Phillips, in an open letter to members, said Labour must “tell the truth” in order to win back voters.
The party suffered its worst defeat since 1935 at last month’s election, losing 59 seats.
The Birmingham Yardley MP said: “The way to begin is to tell the truth. No more pussyfooting or pretending – we have to provide a version of the future that fills our hearts while being rooted in fact.”
In her letter, she said an example of speaking “plainly” was to be upfront with voters on the big issues facing the country, such as social care.
The highest earners should be told that they would have to pay more in taxes to fund the crisis in social care under a Labour administration, she explained.
“When people rightly complain about the state of social care for the elderly, we can tell them there is a way to make it better and give our parents and grandparents the dignity they deserve,” she wrote.
“In fact, the answer is simple – it’s just going to need those that can to chip in a bit more tax. The problems we face become more soluble when we state them plainly.”
A poll carried out by Survation, examining the voting intentions of Labour List readers – a website dedicated to party news – put Ms Phillips in third place, taking 9% of first preferences.
Shadow business secretary Rebecca Long-Bailey is predicted to win overall against Sir Keir Starmer once second preference votes have been taken into account, according to the survey.
Ms Phillips had some tough words for the party’s left-wing members, calling for Labour to become less ideological if it is to have any chance of regaining power for the first time since 2010.
She said the most important thing must be getting into government rather than remaining pure to the left-wing cause.
“If all the Labour Party does is talk, it’s pointless,” she argued.
“To actually make an impact on people’s lives, to give people the things they need to flourish again, we have to act, to make decisions, to change laws – and we can only do that when we’re in power.
“For some, winning has become a trigger word. They think wanting to win suggests a willingness to betray the cause. That losing with purity is somehow more noble.
“But everything great that the Labour Party has ever done – from the NHS to Sure Start – has been achieved only after winning an election.”