We need to increase tax on "unearned" income, i.e. all forms of investment income, scrap/reduce interest allowances/exemptions, investment income surcharge on rental income, interest, dividends, capital gains, etc.
Stop penalising workers and incentivising savers/investors.
We need to review inheritance tax - I'd go for a lower percentage rate and a lower threshold, i.e. something like 10% on everything over £250k per person - a lower rate but on a much broader population base - a low rate like that would mean expensive tax planning wouldn't be as viable so it wouldn't be worth people taking expensive steps to avoid it.
Increase main rate of VAT to maybe 22.5% or even 25% - lots of European countries have higher rates than the UK. Again, the aim being to spread the burden over a wider range, not just workers!
At the same time, bring in incentives for the disabled and unemployed to either get back to work or work longer hours. Stop the immediate loss of benefits and have a "trial" period where benefits remain in place for a few months just in case work doesn't work out. Likewise incentives for everyone to set up self employment or small businesses - same idea - no loss of benefit for the first few months whilst it's being set up and trialled.
We need to create a shift from those with savings/investments towards those we need to be working and growing the economy by doing something, i.e. making things, providing services, etc., and not just spending/saving.