There are some issues you need to consider. Firstly will the leveling compound seep through the joints of the t&g? The compound is also likley to make the chipboard swell with the moisture entering at the joints.
I would recommend putting down a WBP board first, which i warn you is very expensive, however this will provide you with a waterproof base on which to use a leveling or smoothing compound. In addition you could also level up the floor slightly prior. The compound must be suitable for timber floors. For example "Dunlops Universal Floor Leveler" is not suitable, where-as "Ardex Universal" is providing a layer of plywood (WBP) is used first. Check out www.ardex.co.uk for further details.
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