Every bit of glass you place in front of the lens will cause flare. In general, expensive filters cause less flare than cheap ones, and fewer filters cause less flare than more filters.

When you think lens flare, you may think of the circles or shapes that appear in frame as reflections of the sun, but lens flare refers to all unwanted light coming from reflections inside the lens assembly, and can manifest as an overall "haze" or reduction in contrast (exactly like in your example image).

• Make sure your filters are all multi-coated. I'm referring to the anti-reflective coatings. Uncoated filters will cause lots of flare (whole orders of magnitude more flare) while single-coated will still cause noticeably more than multi-coated ones.

  Note: all the elements in your lens itself will be multi-coated on any surface exposed to air. You lose the benefit of multi-coating if you add just one filter/piece of glass in front of it all that isn't multi-coated.

• Make sure the filters are clean. Any dirt or oily smears on them will increase flare or haze.

• For goodness sake, remove the UV filter when putting on the polariser. No need to have more flare than you absolutely need. I'd advise not using a UV filter at all, they are good for nothing other than increasing flare. That, however, seems to be a controversial statement to some photographers, so if you are religiously opposed to shooting without a UV filter then by all means make sure it's a good one and that you take it off when you add a different filter.