Adults in England without an A-level or equivalent qualification will be offered a fully funded college course, the government has announced.
The offer will be available from April and applies to courses offering “skills valued by employers”.
In a speech on Tuesday, the PM will say that, amid the coronavirus pandemic, the government cannot “save every job” but wants to help people find new work.
Labour said the plans would not reverse the impact of “a decade of cuts”.
The government decision comes amid fears that unemployment is set to grow sharply.
The Office for Budget Responsibility has said the unemployment rate could peak at between 9.7% to 13.2% in the next few years. The most recent rate - for May to July - is 4.1%.
In his speech, Boris Johnson will say: “As the chancellor has said, we cannot, alas, save every job - what we can do is give people the skills to find and create new and better jobs.
“We’re transforming the foundations of the skills system so that everyone has the chance to train and retrain.”
The offer of courses to adults without an A-level will be paid for through the National Skills Fund topped up with £2.5bn, the government said.
A full list of available courses will be announced next month.
The government added it wants to make higher education loans more flexible, with the aim of letting people “space out” their learning throughout their life rather than in three or four year blocks, enabling more part-time study.
It said the changes will be backed by investment in college buildings and facilities, including over £1.5bn in capital funding.
Further details will be set out in an education white paper later in the year.
In other plans, small business will be offered financially incentives to take on apprentices and £8m will be spent on skills “boot camps” in West Yorkshire, the South West and Derbyshire and Nottinghamshire to cover sectors like construction and engineering.
This follows pilots in Greater Manchester and the West Midlands that focused on digital skills.
And the government’s online Skills Toolkit, currently providing training in digital and numeracy skills, will be expanded to include 62 additional courses.
Responding to the government’s measures, Labour’s shadow education secretary Kate Green said: “A week ago Labour called for a National Retraining Strategy fit for the crisis Britain faces, but what the government proposes is simply a mix of reheated old policies and funding that won’t be available until April.
“By then many workers could have been out of work for nearly a year, and the Tories still think that they will need to take out loans to get the training they will need to get back in work.”
She added the plans would not give workers “the skills and support they need in the months ahead”.
CBI director general Dame Carolyn Fairbairn said: “The significant unemployment coronavirus is leaving in its wake only accelerates the need for people to develop new skills and adapt to new ways of working.
“The lifetime skills guarantee and flexible loans to support bitesize learning are a strong start but to really shift gears, this must be backed up by meaningful progress on evolving the apprenticeship levy into a flexible skills levy.”
The apprenticeship levy - introduced in 2017 - takes 0.5% of the salary bill from major employers that have an annual pay bill over £3m, with the intention of using the money to improve skills and provide training.
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