Shadow chancellor John McDonnell said he backs raising the threshold on 40p tax for higher earners.
Speaking on The Andrew Marr Show, McDonnell said: "It looks as though the threshold will be increased by the government on Wednesday and we would support that."
Marr suggested it was a tax giveaway, to which McDonnell said: "It is, but it's to people, some of whom need a tax giveaway at the moment, because of the mismanagement of the economy by the Conservative government. It's hitting them hard."
Former chancellor George Osborne raised the 40p threshold to £43,000 from April 2016. In July 2015, people had to start paying the higher rate when they were earning more than £42,385.
McDonnell also reiterated comments made on LBC radio yesterday on the £369m revamp of Buckingham Palace. Despite describing himself as a republican, McDonnell said as the Queen's residence was a "national monument", that needed to be preserved.
"It's a public bill, it's a public monument, it's a heritage building, so we have to invest in it to preserve it," he said, backing the public funding of the project.
However, he "certainly wouldn't send the cheque back", should the Queen opt to chip in on the £369m revamp of Buckingham Palace.
"If the Queen wanted to consider a contribution, I certainly wouldn't send the cheque back, but it does show when we need the money for buildings and maintenance, we can afford it," McDonnell added. He said we should also be tackling "the maintenance problems that ordinary people have got as well".
When pushed on whether he thought the Queen and the Royal family should chip in towards the costs, McDonnell said: "That's for them to consider; we'd welcome it." Though he did add, that "it [Buckingham Palace] would be a nice touch if it was opened up to the public free of charge a bit more as well".
The 10-year refurbishment is due to be funded by an increase in the annual Sovereign Grant, from £43m to £71m. The Treasury has said an "urgent overhaul" is needed to prevent fire and flood damage.