"... consider new options such as a land value tax, to ensure local government has sustainable funding for the long term."
Looking at the name 'Land Value Tax', you might think this is only aimed at house builders with 'brownfield' sites or at footballers wanting to build a big new 'mansion' in the countryside. But according to the London think-tank which proposes it, it would be aimed at every ordinary home-owner, being levied on even the smallest garden or patch of grass in the land. Their website says it would require a Domesday Book -style army of inspectors, snooping around each and every plot and garden to mark it down for the Tax.
Note that there's no talk in the manifesto of the new Tax being a replacement for the Council Tax. It would probably be introduced softly as 'part of a mix', with the Garden Tax being the lesser of the two taxes. But as Labour (once again) inevitably runs out other people's money, the Land Value Tax would almost certainly become a larger and larger addition to the existing Council Tax. A 2015 report from a Labour Party group suggests the Tax would be 3% of a brownfield plot's theoretical future value, but that would only be an "initial" introductory rate intended to get people used to the idea. There would also be a lesser percentage, perhaps 0.85% to start with, on the land around and under homes.
The proposed Tax would include agricultural land as well, so presumably large urban allotments could be in for an annual tax-demand whammy. Because allotments would be assessed on what ground-rent could theoretically be had, if houses were built there in the future, not on the inspector weighing your current crop of potatoes and strawberries. It'd be a Tax "on the value of land if it were to be developed to its possible permitted planning use". So Labour thinks it has found a way to tax the future, basically. Not that there would be much of a future left to tax, under a Labour government.
It appears the only people who might see major benefits could be those in high-rise flats. But even people in flats may even be no better off, because there would be no way they could sell off the surrounding gardens and car-park and thus avoid the extra Tax. And you can also be fairly sure that the new Tax would be taken as an excuse to hike up the existing ground-rent and service-charges, and it would also likely also feed through to the monthly rent and deposits.
Anyway, Horticulture Week magazine has an even-handed report on the details of the proposed new Tax, if you're interested in reading more. (The first read of an article is free, then they want $s).
Lastly I'd also note that, down in nearby Birmingham, the Labour city council is already eagerly attacking those with large gardens. It's imposing a charge of £35 every time a bag of 'green waste' is collected from a house.